Posterior spinal fixation screws

ABSTRACT

The present disclosure includes bone screws and assemblies thereof for surgical procedures of the spine including but not limited to posterior spinal fixation procedures.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a non-provisional of, and claims the benefitof priority of U.S. Provisional Patent Application Ser. No. 62/851,100filed May 22, 2019, the entire contents of which are incorporated hereinby reference.

TECHNICAL FIELD

The present disclosure relates generally to spinal implants.

BACKGROUND OF THE DISCLOSURE

The spine is critical in human physiology for mobility, support, andbalance. Spinal injuries can be debilitating or catastrophic topatients. Even small irregularities in the spine can cause devastatingpain and loss of coordination.

Surgical procedures on the spine can often include application of boneanchors or bone screws that are connected by rigid spinal rods locked toeach bone screw. The bone screws can often include an anchor componentand a rod-housing component (or “tulip”) that is often coupled to theanchor component in a manner that permits angular adjustability of thetulip relative to the anchor component.

SUMMARY OF THE DISCLOSURE

Bone screws and spinal rods are widely used in surgical procedures ofthe spine such as posterior spinal fixation. In certain spinalprocedures, when bone screws are implanted in the desired positions, aspinal rod is seated in each tulip or receiver and locked in position.The angular adjustability of each receiver is also locked, eitherthrough the locking of the spinal rod, or independently thereof, to thusfix the connected vertebrae relative to each other. Bone screwconfigurations which allow increased angulation of the receiver relativeto the bone screw shank are useful in certain situations where anincreased pivot angle is needed (e.g. where there is an acute anglebetween the anchor component and rod trajectories). However,configurations that permit the increased angulation also tend to reducethe strength of the connection between the anchor component androd-housing component. Therefore, an urgent need exists for new andimproved bone screws with increased angulation housings but without thereduction in connection strength suffered in current solutions.

Existing bone screws used in spinal procedures can only be connectedusing a spinal rod locked in each of the receivers. There is an urgentneed for improved bone screws that can be coupled or fixed in movementin specified direction(s) with freedom to move in other directions, andmaintained ability to be connected to the spinal rod. Such improved bonescrews can increase flexibility in surgical applications that needscomplex deformity and involves trauma. There is also a need for twospinal rod connections to be included in a single bone screw in order torender flexibility in building a construct containing multiple screwsand spinal rods.

In some spinal procedures, spinal rods with circular cross section maypresent difficulty in centering in the rod channel, limited strength andrigidity when the profile of the spinal rod is limited. Existing spinalrods may also only provide small contact surface with the closure top orset screw during lock down. Thus, there is a need for improvement of theexisting spinal-rods with circular cross sections.

In certain spinal procedures focusing on ilium, sacrum, or sacroiliacregions, it is necessary to include either a sharp bend in the spinalrod to join with bone screws at superior levels or usage of a secondaryrod or offset tulip connector. There is an urgent need to reduce thenumber of different connectors/screws and overall bulk of the constructwhile making a more rigid construct by reducing the number of connectionpoints that can fail.

In some spinal procedures, increased angulation of the bone screw shankrelative to the receiver may be desired. In applications related toiliac, sacrum, and/or pelvic regions, a marginal increase in tulipheight can be tolerated for increased angulation that is essential tospecific spinal procedures.

With traditional bone screws, once the spinal rod is placed and lockeddown, the construct is locked and the shank relative to the receiver islocked. However, in certain spinal procedures, e.g., a neuromuscularscoliosis case, there is a need for a simpler solution that can lock thebone screw(s) with or without a rod placed in the tulip rod slot andwith or without a lock screw in the tulip. There is also a need toremove the step to provisionally lock the screw using external tools,but still maintain the capability that can be provided by thetraditional provisional locking step, thereby making the proceduresimpler to perform and more efficient.

Disclosed herein are bone screws and bone screw assemblies that addressone or more needs for improvement on existing spinal implants,especially bone screws and their assemblies. The bone screws disclosedherein can advantageously provide better, simpler, more reliable, andmore accurate performance in various spinal procedures.

In one aspect, disclosed herein is a bone screw comprising: a bone screwshank comprising a shank head; a receiver comprising: a base having acavity therewithin, the cavity configured to securely receive the shankhead; a pair of arms extending upwardly from the base; a rod channeldefined between the pair of arms; and a lateral rod integral to thereceiver and extending laterally away from the receiver.

In another aspect, disclosed herein is a bone screw assembly comprising:a first bone screw, the first bone screw comprising a first receiverhaving a first base with a first cavity therewithin, the first cavityconfigured to securely receive a first bone screw shank head; a firstpair of arms extending upwardly from the base; a first rod channeldefined between the first pair of arms; and a first lateral rod integralto the first receiver and extending laterally away from the firstreceiver; a second bone screw, the second bone screw comprising a secondreceiver having a second base with a second cavity therewithin, thesecond cavity configured to securely receive a second bone screw shankhead; a second pair of arms extending upwardly from the second base; asecond rod channel defined between the second pair of arms; and a secondlateral rod integral to the second receiver and extending laterally awayfrom the second receiver; and a rod to rod connector configured tosecurely receive the first lateral rod in a first bore and the secondlateral rod in a second bore.

In another aspect, disclosed herein is a bone screw comprising: a bonescrew shank comprising a shank head; a dual-head receiver comprising: afirst receiver comprising a first base having a cavity therewithin, thecavity configured to securely receive the shank head; a first pair ofarms extending upwardly from the first base; a first rod channel definedbetween the first pair of arms; a second receiver comprising a secondbase having a second rod channel defined between a second pair of arms;and a connection between the first receiver and the second receiver.

In yet another aspect, disclosed herein is a bone screw assemblycomprising: a first bone screw comprising: a first bone screw shankcomprising a first shank head; a first dual-head receiver comprising: afirst receiver comprising a first base having a first cavitytherewithin, the first cavity configured to securely receive the firstshank head; a first pair of arms extending upwardly from the first base;a first rod channel defined between the first pair of arms; a secondreceiver comprising a second base having a second rod channel definedbetween a second pair of arms; and a first connection between the firstreceiver and the second receiver; a second bone screw comprising: asecond bone screw shank comprising a second shank head; a seconddual-head receiver comprising: a third receiver comprising a third basehaving a second cavity therewithin, the second cavity configured tosecurely receive the second shank head; a third pair of arms extendingupwardly from the third base; a third rod channel defined between thethird pair of arms; a fourth receiver comprising a fourth base having afourth rod channel defined between a fourth pair of arms; and a secondconnection between the third receiver and the third receiver; and alateral rod securely received in the second rod channel and the fourthrod channel thereby securely connecting the first bone screw and thesecond bone screw.

In yet another aspect, disclosed herein is a bone screw comprising: abone screw shank comprising a shank head; a dual-head receivercomprising: a first receiver comprising a first base having a cavitytherewithin, the cavity configured to securely receive the shank head; afirst pair of arms extending upwardly from the first base; a first rodchannel defined between the first pair of arms; a second receivercomprising a second base having a second rod channel defined between asecond pair of arms; and a connection between the first receiver and thesecond receiver.

In yet another aspect, disclosed herein is a bone screw assemblycomprising: a first bone screw comprising: a first bone screw shankcomprising a first shank head; a first dual-head receiver comprising: afirst receiver comprising a first base having a first cavitytherewithin, the first cavity configured to securely receive the firstshank head; a first pair of arms extending upwardly from the first base;a first rod channel defined between the first pair of arms; a secondreceiver comprising a second base having a second rod channel definedbetween a second pair of arms; and a first connection between the firstreceiver and the second receiver; a second bone screw comprising: asecond bone screw shank comprising a second shank head; a seconddual-head receiver comprising: a third receiver comprising a third basehaving a second cavity therewithin, the second cavity configured tosecurely receive the second shank head; a third pair of arms extendingupwardly from the third base; a third rod channel defined between thethird pair of arms; a fourth receiver comprising a fourth base having afourth rod channel defined between a fourth pair of arms; and a secondconnection between the third receiver and the third receiver; and a rodsecurely received in the second rod channel and the fourth rod channelthereby securely connecting the first bone screw and the second bonescrew.

In yet another aspect, disclosed herein is a spinal rod, comprising: anelongate body with a non-circular cross section, wherein elongate bodyis configured to be slidely insertable into a spinal rod channel of abone screw receiver, and is configured to be secured within the spinalrod channel of the bone screw receiver by a closure top pressing againstthe elongate body, wherein the non-circular cross section comprises aflat top edge, two flat side edges, and a curved V-shaped bottom edge.

In yet another aspect, disclosed herein is a spinal rod, comprising: anelongate body with a non-circular cross section, wherein elongate bodyis configured to be slidely insertable into a spinal rod channel of abone screw receiver, and is configured to be secured within the spinalrod channel of the bone screw receiver by a closure top pressing againstthe elongate body, wherein the non-circular cross section comprises acurved top edge, two curved side edges, and a curved bottom edge.

In yet another aspect, disclosed herein is a spinal rod, comprising: anelongate body with a non-circular cross section, wherein elongate bodyis configured to be slidely insertable into a spinal rod channel of abone screw receiver, and is configured to be secured within the spinalrod channel of the bone screw receiver by a closure top pressing againstthe elongate body, wherein the non-circular cross section comprises aflat top edge and a curved or flat bottom edge.

In yet another aspect, disclosed herein is a bone screw comprising: abone screw shank comprising a shank head; a dual-head receivercomprising: a first receiver comprising a first base having a cavitytherewithin, the cavity configured to securely receive the shank head; afirst top having an opening to receive a locking element therewithinthereby locking the shank head within the cavity; a second receivercomprising a second base having a rod channel defined between a pair ofarms; and a connection between the first receiver and the secondreceiver.

In yet another aspect, disclosed herein is a bone screw comprising: abone screw shank comprising a shank head; a receiver comprising a basehaving a cavity therewithin, the cavity configured to accept insertionof the shank head from a bottom of the receiver; a pair of armsextending upwardly from the base; and a rod channel defined between thepair of arms; a load ring configured to be bottom-loaded into thereceiver prior to the insertion of the shank head, wherein the load ringcomprises a pair of legs connected by two concave surfaces at itsproximal side; and a clip ring configured to be inserted into a groovelocated in an inner surface at or near the bottom of the receiver in anopen position when the load ring and the shank head are pushed proximalto a locking position, wherein in the open position, each of the pair oflegs faces an opening of the rod channel and each of the concavesurfaces is aligned with one of the pair of arms.

In yet another aspect, disclosed herein is a method of assembly of abone screw, the method comprising: providing a bone screw shankcomprising a shank head; providing a receiver comprising a base having acavity therewithin, the cavity configured to securely accept insertionof the shank head from a bottom of the receiver; a pair of armsextending upwardly from the base; and a rod channel defined between thepair of arms; providing a load ring configured to be bottom-loaded intothe receiver prior to the insertion of the shank head, wherein the loadring comprises a pair of legs connected by two concave surfaces at itsproximal side; and providing a clip ring configured to be inserted intoa groove located in an inner surface at or near the bottom of thereceiver thereby pushing the load ring and the shank head into an openposition that is proximal to a locking position, wherein in the openposition, each of the pair of legs is at least partly facing an openingof the rod channel and each of the concave surfaces are aligned with thepair of arms.

In yet another aspect, disclosed herein is a method of assembly of abone screw, the method comprising: loading a load ring from a bottom endof a receiver of the bone screw through a cavity thereof prior to theinsertion of the shank head, wherein loading the load ring comprisestwisting the load ring so that each of two opposing concave surfaces ata proximal surface of the load ring is aligned with an upwardlyextending arm of the receiver and pushing the load ring proximally;inserting the shank head into the receiver from the bottom end thereoftill access to a groove in an inner surface of the receiver at or near adistal end thereof is open; inserting a clip ring into the groove in theinner surface of the receiver; pushing the load ring and the shank headdistally; and twisting the load ring in to a locked position so thateach of the two concave surfaces at the top surface of the load ring isaligned with an opening of the rod channel of the receiver, wherein theload ring and the shank head is locked from distal movement.

In yet another aspect, disclosed herein is a bone screw comprising: abone screw shank comprising a shank head; a receiver comprising a basehaving a cavity therewithin, the cavity configured to securely acceptinsertion of the shank head from a top of the receiver; a pair of armsextending upwardly from the base; and a rod channel defined between thepair of arms, wherein the base comprises a recess formed in a bottomsurface thereof, wherein the base and the recess are shaped and sized toallow angulation in a range of about 0 degrees to about 60 degrees in afirst lateral direction and prevent angulation of greater than about 0degrees in a second lateral direction opposite the first lateraldirection; and a load ring configured to be top-loaded into the receiversubsequent to the insertion of the shank head, wherein the load ringcomprises a pair of legs connected by two concave surfaces at itsproximal side.

In yet another aspect, disclosed herein is a bone screw assemblycomprising: a bone screw shank comprising a shank head; a receivercomprising a base having a cavity therewithin, the cavity configured tosecurely accept insertion of the shank head from a top of the receiver;a pair of arms extending upwardly from the base; and a rod channeldefined between the pair of arms; a compression element configured to betop-loaded into the receiver subsequent to the insertion of the shankhead, wherein the compression element comprises a pair of legs connectedby two concave surfaces at its proximal side, and a lock screwconfigured to be top-loaded into the receiver thereby locking the shankhead relative to the receiver.

INCORPORATION BY REFERENCE

All publications and patent applications mentioned in this specificationare herein incorporated by reference to the same extent as if eachindividual publication or patent application was specifically andindividually indicated to be incorporated by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe appended claims. A better understanding of the features andadvantages of the present invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings of which:

FIG. 1 shows an exemplary embodiment of the bone screws; in this case, abone screw with a lateral rod in a perspective view, in accordance withthe embodiments herein;

FIG. 2 shows an exemplary embodiment of the receiver of the bone screwin FIG. 1, in accordance with the embodiments herein;

FIG. 3 shows an exemplary embodiment of a cross section from D-D′ of thebone screw in FIGS. 1-2, in accordance with the embodiments herein;

FIG. 4 shows an exemplary embodiment of a bone screw assembly includingtwo bone screws in FIGS. 1-3 in a perspective view, in accordance withembodiments herein;

FIG. 5 shows an exemplary embodiment of the bone screw assembly in FIG.4 in a top view, in accordance with embodiments herein;

FIGS. 6A-6D show exemplary embodiments of the bone screws disclosedherein; in this case, a uniplanar bone screw that allow the bone screwshank to rotate symmetrically in two opposite directions, in accordancewith embodiments herein;

;

FIGS. 7-8 show exemplary embodiments of a dual-head bone screw indifferent views, in accordance with embodiments herein;

FIG. 9 shows a cross section view of the dual-head bone screw in FIGS.7-8, in accordance with embodiments herein;

FIG. 10 shows an exemplary embodiment of a bone screw assemblycontaining two dual-head bone screws in FIGS. 7-9 in a perspective view,in accordance with embodiments herein;

FIG. 11 shows an exemplary embodiment of a bone screw assemblycontaining two dual-head bone screws in FIGS. 7-9 in a cross-sectionalview, in accordance with embodiments herein;

FIG. 12 shows an exemplary embodiment of a dual-head bone screw, inaccordance with embodiments herein;

FIG. 13 shows a cross section of the dual-head bone screw in FIG. 12, inaccordance with embodiments herein;

FIG. 14 shows an exemplary embodiment of a receiver of a dual-head bonescrew disclosed herein, in accordance with embodiments herein;

FIGS. 15A-15H show exemplary embodiment of the spinal rod with anon-circular cross section, in accordance with embodiments herein;

FIGS. 16A-16D show exemplary cross section of spinal rods with thecorresponding calculation of polar moment of inertia for torsion of thespinal rods, in accordance with embodiments herein;

FIGS. 17A-17B show exemplary embodiments of the bone screws disclosedherein, in accordance with embodiments herein;

FIG. 18 shows a cross-sectional view of the bone screw in FIGS. 17A-17B,in accordance with embodiments herein;

FIGS. 19A-19B show exemplary embodiments of the dual-head bone screwsdisclosed herein; in this case, a perspective view (FIG. 19A) and sideview (FIG. 19B) of the dual-head bone screws with the connection betweenthe two receivers integral to the first receiver but rotatable and/ortranslatable relative to the second receiver; and

FIGS. 19C-19D show exemplary embodiments of the dual-head bone screwsdisclosed herein; in this case, top views of the dual-head bone screwswith a connection that is rotatable and/or translatable relative to oneof the two receivers;

FIG. 20 shows an exemplary embodiment of the bone screws disclosedherein, in accordance with embodiments herein;

FIGS. 21A-21B show exemplary embodiments of the bone screw in FIG. 20 incross-sectional views, in accordance with embodiments herein;

FIGS. 22A-22I show exemplary embodiments of the bone screws disclosedherein during the process of assembly thereof, in accordance withembodiments herein;

FIGS. 23A-23C show exemplary embodiments of the bone screw after thebone screw in FIGS. 20-22I is assembled, in accordance with embodimentsherein;

FIGS. 24-28 show exemplary embodiments of the bone screws disclosedherein; in this case, a bone screw that provides a hard stop and atactile feedback when the longitudinal axis of the receiver is alignedwith the longitudinal axis of the shank, in accordance with embodimentsherein;

FIGS. 29-31 show exemplary embodiments of the receiver of the bonescrews disclosed herein in different views, in accordance withembodiments herein;

FIG. 32 shows an exemplary embodiment of the load ring of the bonescrews disclosed herein in a perspective view, in accordance withembodiments herein;

FIGS. 33A-33D show exemplary embodiments of the bone screws withdifferent bone screw shanks, in accordance with embodiments herein;

FIGS. 34A-34B show exemplary embodiments of the bone screws; in thiscase, the receiver and the bone screw shank during top-loading assembly,in accordance with embodiments herein;

FIGS. 35A-35G show exemplary embodiments of the bone screws disclosedherein; in this case, the compression element during top-loadingassembly of the bone screw, in accordance with embodiments herein;

FIGS. 35H-35L show exemplary embodiments of the bone screws disclosedherein, in this case, the lock screw, in accordance with embodimentsherein;

FIG. 36 shows an exemplary embodiment of the bone screws disclosedherein, in this case, the lock screw, in accordance with embodimentsherein;

FIGS. 37-38 show exemplary embodiments of the bone screws disclosedherein, in this case, the receiver and the shank head bone screwdisclosed herein, in accordance with embodiments herein;

FIG. 39A shows an exemplary embodiment of the dual-head bone screwsdisclosed herein; in this case, a perspective view of the dual-head bonescrews with two spinal rod channels at different levels along theproximal to distal direction;

FIG. 39B shows an exemplary embodiment of the dual-head bone screwsdisclosed herein; in this case, a top view of the dual-head bone screwin FIG. 39A with a connection that includes a curved portion;

FIG. 40A shows an exemplary embodiment of the dual-head bone screwsdisclosed herein; in this case, a perspective view of the dual-head bonescrews with two spinal rod channels that extend in directions that aresubstantially parallel to each other;

FIG. 40B shows an exemplary embodiment of the dual-head bone screw shownin FIG. 40A; in this case, a top view of the dual-head bone screws witha connection that extends in a direction that is titled from a directionof extension of the first rod channel or the second rod channel;

FIGS. 41A-41B show exemplary embodiments of the dual-head bone screwsdisclosed herein; in this case, a perspective view (FIG. 41A) and sideview (FIG. 41B) of the dual-head bone screws with the longitudinal axesof the two receivers form an acute angle therebetween; and

FIG. 41C shows an exemplary embodiment of the dual-head bone screwsdisclosed herein; a top view of the dual-head bone screws with aconnection that extends in a direction that is titled from a directionof extension of the first rod channel or the second rod channel.

DETAILED DESCRIPTION OF THE DISCLOSURE

In certain embodiments, disclosed herein is a bone screw comprising: abone screw shank comprising a shank head; a receiver comprising: a basehaving a cavity therewithin, the cavity configured to securely receivethe shank head; a pair of arms extending upwardly from the base; a rodchannel defined between the pair of arms; and a lateral rod integral tothe receiver and extending laterally away from the receiver. In someembodiments, the lateral rod extends laterally from an outer surface ofone of the pair of arms. In some embodiments, the receiver comprises alongitudinal axis extending through a bottom end of the base toward atop end of the pair of arms, and wherein the lateral rod extendsperpendicular to the longitudinal axis of the receiver. In someembodiments, the lateral rod is perpendicular to a first direction ofextension of the rod channel, or wherein the lateral rod is tilted by anangle from the first direction of extension of the rod channel. In someembodiments, the lateral rod is straight, curved, or bent. In someembodiments, the lateral rod comprises a size that is configured to bereceived in a rod to rod connector or a rod channel of a second bonescrew. In some embodiments, the lateral rod comprises a cross-sectionalshape that is identical to a spinal rod that is configured to bereceived in the rod channel of the bone screw. In some embodiments, thelateral rod comprises a substantially cylindrical shape. In someembodiments, the receiver comprising a tool engagement groove at anouter surface of the pair of arms at or near a top end thereof, andwherein a top edge of the lateral rod is distal to the tool engagementgroove. In some embodiments, a bottom edge of the lateral rod isproximal to a bottom surface of the base. In some embodiments, the bonescrew is a poly-axial screw.

In certain embodiments, disclosed herein is a bone screw assemblycomprising: a first bone screw, the first bone screw comprising a firstreceiver having a first base with a first cavity therewithin, the firstcavity configured to securely receive a first bone screw shank head; afirst pair of arms extending upwardly from the base; a first rod channeldefined between the first pair of arms; and a first lateral rod integralto the first receiver and extending laterally away from the firstreceiver; a second bone screw, the second bone screw comprising a secondreceiver having a second base with a second cavity therewithin, thesecond cavity configured to securely receive a second bone screw shankhead; a second pair of arms extending upwardly from the second base; asecond rod channel defined between the second pair of arms; and a secondlateral rod integral to the second receiver and extending laterally awayfrom the second receiver; and a rod to rod connector configured tosecurely receive the first lateral rod in a first bore and the secondlateral rod in a second bore. In some embodiments, the first bore andthe second bore of the rod to rod connector are substantially parallelto each other. In some embodiments, the first rod channel and the secondrod channel are configured to receive a longitudinal rod therewithin. Insome embodiments, the first bone screw is anchored in a first vertebralbone, and the second bone screw is anchored in a second vertebral bone.In some embodiments, the first bone screw or the second bone screw is apoly-axial screw. In some embodiments, the rod to rod connectorcomprises a first opening at a top thereof, the first opening connectedto the first bore. In some embodiments, the first opening is configuredto receive a closure top that presses against the first lateral rodthereby securing the first lateral rod to the rod to rod connector. Insome embodiments, the rod to rod connector comprises a second opening ata top thereof, the second opening connected to the second bore. In someembodiments, the second opening is configured to receive a closure topthat presses against the second lateral rod thereby securing the secondlateral rod to the rod to rod connector.

In certain embodiments, disclosed herein is a bone screw comprising: abone screw shank comprising a shank head; a dual-head receivercomprising: a first receiver comprising a first base having a cavitytherewithin, the cavity configured to securely receive the shank head; afirst pair of arms extending upwardly from the first base; a first rodchannel defined between the first pair of arms; a second receivercomprising a second base having a second rod channel defined between asecond pair of arms; and a connection between the first receiver and thesecond receiver. In some embodiments, the connection is integral to thefirst and second receivers, or the connection is integral to one of thefirst or second receiver but movable relative to the other one of thefirst or second receiver. In some embodiments, the first rod channelextends in a first direction, and the second rod channel extends in asecond direction substantially perpendicular to the first direction, orwherein the second rod channel extends in a second direction that istilted by an angle from the first direction. In some embodiments, atleast part of the first pair of arms face an opening of the secondchannel. In some embodiments, a bottom surface of the second base isproximal to a bottom surface of the first base. In some embodiments, thefirst receiver comprises a longitudinal axis extending in a proximal todistal direction, and wherein the connection between the first receiverand the second receiver extends substantially perpendicular to thelongitudinal axis of the first receiver. In some embodiments, theconnection between the first receiver and the second receiver extends ina direction that is perpendicular to a direction of extension from thefirst rod channel or tilted by an angle from the direction of extensionfrom the first rod channel. In some embodiments, the connection betweenthe first receiver and the second receiver extends laterally from anouter surface of one of the first pair of arms. In some embodiments, theconnection between the first receiver and the second receiver extendslaterally from an outer surface of an opening of the second rod channel.In some embodiments, the first rod channel and the second rod channelcomprise an identical size or shape. In some embodiments, the firstreceiver comprising a first tool engagement groove at an outer surfaceof the first pair of arms at or near a top surface thereof, and whereina top edge of the connection between the first receiver and the secondreceiver is distal to the first tool engagement groove. In someembodiments, the second receiver comprising a second tool engagementgroove at an outer surface of the second pair of arms at or near a topsurface thereof, and wherein a top edge of the connection between thefirst receiver and the second receiver is distal to the second toolengagement groove. In some embodiments, a bottom surface of theconnection between the first receiver and the second receiver isproximal to a bottom surface of the first base. In some embodiments, thefirst receiver is configured to receive a first closure top that pressesagainst a first rod within the first rod channel thereby securing thefirst rod therewithin. In some embodiments, the second receiver isconfigured to receive a second closure top that presses against a secondrod within the second rod channel thereby securing the second rodtherewithin. In some embodiments, the first receiver comprises a U-shapeopening defined by at least part of an edge of each of the first pair ofarms. In some embodiments, the second receiver comprises a U-shapeopening defined by at least part of an edge of each of the second pairof arms. In some embodiments, the connector is narrower than the firstreceiver along a direction of extension of the first rod channel or thesecond rod channel. In some embodiments, second receiver is shorter thanthe first receiver along a proximal to distal direction. In someembodiments, the second rod channel extends laterally beyond an edge ofeach of the second pair of arms. In some embodiments, the second rodchannel extends laterally beyond a lateral edge of the second receiver.The bone screw can be a polyaxial screw. In some embodiments, the secondrod channel comprises a half-moon opening at a lateral edge of thesecond receiver. In some embodiments, the first and second rod channelsare at an identical level along the proximal to distal direction. Insome embodiments, the first and second rod channels are at two differentlevels along the proximal to distal direction.

In certain embodiments, disclosed herein is a bone screw assemblycomprising: a first bone screw comprising: a first bone screw shankcomprising a first shank head; a first dual-head receiver comprising: afirst receiver comprising a first base having a first cavitytherewithin, the first cavity configured to securely receive the firstshank head; a first pair of arms extending upwardly from the first base;a first rod channel defined between the first pair of arms; a secondreceiver comprising a second base having a second rod channel definedbetween a second pair of arms; and a first connection between the firstreceiver and the second receiver; a second bone screw comprising: asecond bone screw shank comprising a second shank head; a seconddual-head receiver comprising: a third receiver comprising a third basehaving a second cavity therewithin, the second cavity configured tosecurely receive the second shank head; a third pair of arms extendingupwardly from the third base; a third rod channel defined between thethird pair of arms; a fourth receiver comprising a fourth base having afourth rod channel defined between a fourth pair of arms; and a secondconnection between the third receiver and the third receiver; and alateral rod securely received in the second rod channel and the fourthrod channel thereby securely connecting the first bone screw and thesecond bone screw. In some embodiments, the first rod channel extends ina first direction, and the second rod channel extends in a seconddirection substantially perpendicular to the first direction or at anacute angle to the first direction. In some embodiments, at least partof the first pair of arms face an opening of the second channel. In someembodiments, a bottom surface of the second base is proximal to a bottomsurface of the first base. In some embodiments, the first receivercomprises a longitudinal axis extending in a proximal to distaldirection, and wherein the connection between the first receiver and thesecond receiver extends substantially perpendicular to the longitudinalaxis of the first receiver. In some embodiments, the connection betweenthe first receiver and the second receiver extends laterally from anouter surface of one of the first pair of arms. In some embodiments, theconnection between the first receiver and the second receiver extendslaterally from an outer surface of an opening of the second rod channel.In some embodiments, the first rod channel and the second rod channelcomprise an identical size or shape. In some embodiments, the firstreceiver comprising a first tool engagement groove at an outer surfaceof the first pair of arms at or near a top surface thereof, and whereina top edge of the connection between the first receiver and the secondreceiver is distal to the first tool engagement groove. In someembodiments, the second receiver comprising a second tool engagementgroove at an outer surface of the second pair of arms at or near a topsurface thereof, and wherein a top edge of the connection between thefirst receiver and the second receiver is distal to the second toolengagement groove. In some embodiments, a bottom surface of theconnection between the first receiver and the second receiver isproximal to a bottom surface of the first base. In some embodiments, thefirst receiver is configured to receive a first closure top that pressesagainst a first rod within the first rod channel thereby securing thefirst rod therewithin. In some embodiments, the second receiver isconfigured to receive a second closure top that presses against a secondrod within the second rod channel thereby securing the second rodtherewithin. In some embodiments, the first receiver comprises a U-shapeopening defined by at least part of an edge of each of the first pair ofarms. In some embodiments, the second receiver comprises a U-shapeopening defined by at least part of an edge of each of the second pairof arms. In some embodiments, the connector is narrower than the firstreceiver. In some embodiments, second receiver is shorter than the firstreceiver along a proximal to distal direction. In some embodiments, thesecond rod channel extends laterally beyond an edge of each of thesecond pair of arms. In some embodiments, the second rod channel extendslaterally beyond a lateral edge of the second receiver. The bone screwcan be a polyaxial screw. In some embodiments, the second rod channelcomprises a half-moon opening at a lateral edge of the second receiver.In some embodiments, the first connection is integral to the first andsecond receivers, or the first connection is integral to one of thefirst or second receiver but movable relative to the other one of thefirst or second receiver. In some embodiments, the second connection isintegral to the third and fourth receivers, or the connection isintegral to one of the first or second receiver but movable relative tothe other one of the first or second receiver.

In certain embodiments, disclosed herein is a bone screw comprising: abone screw shank comprising a shank head; a dual-head receivercomprising: a first receiver comprising a first base having a cavitytherewithin, the cavity configured to securely receive the shank head; afirst pair of arms extending upwardly from the first base; a first rodchannel defined between the first pair of arms; a second receivercomprising a second base having a second rod channel defined between asecond pair of arms; and a connection between the first receiver and thesecond receiver. In some embodiments, the connection is integral to thefirst and second receivers, or the connection is integral to one of thefirst or second receiver but movable relative to the other one of thefirst or second receiver. In some embodiments, the first rod channelextends in a first direction, and the second rod channel extends in asecond direction substantially parallel to the first direction. In someembodiments, the first rod channel extends in a first direction, and thesecond rod channel extends in a second direction that is tilted by anangle with the first direction. In some embodiments, the first rodchannel and the second rod channel are at an identical level along aproximal to distal direction. In some embodiments, the first rod channeland the second rod channel are at two different levels along a proximalto distal direction. In some embodiments, the first pair of arms facethe second pair of arms. In some embodiments, a bottom surface of thesecond base is proximal to a bottom surface of the first base. In someembodiments, the first receiver comprises a longitudinal axis extendingin a proximal to distal direction, and wherein the connection betweenthe first receiver and the second receiver extends substantiallyperpendicular to the longitudinal axis of the first receiver. In someembodiments, the connection between the first receiver and the secondreceiver extends in a direction that is perpendicular to a direction ofextension of the first rod channel or tilted by an angle from thedirection of extension of the first rod channel. In some embodiments,the connection between the first receiver and the second receiverextends laterally from an outer surface of one of the first pair ofarms. In some embodiments, the connection between the first receiver andthe second receiver extends laterally from an outer surface of one ofthe second pair of arms. In some embodiments, the connection between thefirst receiver and the second receiver extends laterally from an outersurface of the first base to an outer surface of the second base. Insome embodiments, the first rod channel and the second rod channelcomprise an identical size or shape. In some embodiments, the firstreceiver comprising a first tool engagement groove at an outer surfaceof the first pair of arms at or near a top surface thereof, and whereina top edge of the connection between the first receiver and the secondreceiver is proximal to the first tool engagement groove. In someembodiments, the second receiver comprising a second tool engagementgroove at an outer surface of the second pair of arms at or near a topsurface thereof, and wherein a top edge of the connection between thefirst receiver and the second receiver is distal to the second toolengagement groove. In some embodiments, a bottom surface of theconnection between the first receiver and the second receiver isproximal to a bottom surface of the first base. In some embodiments, thefirst receiver comprises a proximal opening that is configured toreceive a first closure top that presses against a first rod within thefirst rod channel thereby securing the first rod therewithin. In someembodiments, the second receiver comprises a proximal opening that isconfigured to receive a second closure top that presses against a secondrod within the second rod channel thereby securing the second rodtherewithin. In some embodiments, the first receiver comprises a U-shapeopening defined by at least part of an edge of each of the first pair ofarms. In some embodiments, the second receiver comprises a U-shapeopening defined by at least part of an edge of each of the second pairof arms. In some embodiments, the second receiver is shorter than thefirst receiver along a proximal to distal direction. In someembodiments, the first rod channel and the second rod channel are at anidentical level along a proximal to distal direction. In someembodiments, the bone screw is a polyaxial screw.

In certain embodiments, disclosed herein is a bone screw assemblycomprising: a first bone screw comprising: a first bone screw shankcomprising a first shank head; a first dual-head receiver comprising: afirst receiver comprising a first base having a first cavitytherewithin, the first cavity configured to securely receive the firstshank head; a first pair of arms extending upwardly from the first base;a first rod channel defined between the first pair of arms; a secondreceiver comprising a second base having a second rod channel definedbetween a second pair of arms; and a first connection between the firstreceiver and the second receiver; a second bone screw comprising: asecond bone screw shank comprising a second shank head; a seconddual-head receiver comprising: a third receiver comprising a third basehaving a second cavity therewithin, the second cavity configured tosecurely receive the second shank head; a third pair of arms extendingupwardly from the third base; a third rod channel defined between thethird pair of arms; a fourth receiver comprising a fourth base having afourth rod channel defined between a fourth pair of arms; and a secondconnection between the third receiver and the third receiver; and a rodsecurely received in the second rod channel and the fourth rod channelthereby securely connecting the first bone screw and the second bonescrew. In some embodiments, the first rod channel extends in a firstdirection, and the second rod channel extends in a second directionsubstantially parallel to the first direction. In some embodiments, thefirst pair of arms faces the second pair of arms. In some embodiments, abottom surface of the second base is proximal to a bottom surface of thefirst base. In some embodiments, the first receiver comprises alongitudinal axis extending in a proximal to distal direction, andwherein the connection between the first receiver and the secondreceiver extends substantially perpendicular to the longitudinal axis ofthe first receiver. In some embodiments, the connection between thefirst receiver and the second receiver extends laterally from an outersurface of one of the first pair of arms. In some embodiments, theconnection between the first receiver and the second receiver extendslaterally from an outer surface of one of the second pair of arms. Insome embodiments, the first rod channel and the second rod channelcomprise an identical size or shape. In some embodiments, the firstreceiver comprising a first tool engagement groove at an outer surfaceof the first pair of arms at or near a top surface thereof, and whereina top edge of the connection between the first receiver and the secondreceiver is proximal to the first tool engagement groove. In someembodiments, the second receiver comprising a second tool engagementgroove at an outer surface of the second pair of arms at or near a topsurface thereof, and wherein a top edge of the connection between thefirst receiver and the second receiver is proximal to the second toolengagement groove. In some embodiments, a bottom surface of theconnection between the first receiver and the second receiver isproximal to a bottom surface of the first base. In some embodiments, thefirst receiver is configured to receive a first closure top that pressesagainst a first rod within the first rod channel thereby securing thefirst rod therewithin. In some embodiments, the second receiver isconfigured to receive a second closure top that presses against a secondrod within the second rod channel thereby securing the second rodtherewithin. In some embodiments, the first receiver comprises a U-shapeopening defined by at least part of an edge of each of the first pair ofarms. In some embodiments, the second receiver comprises a U-shapeopening defined by at least part of an edge of each of the second pairof arms. In some embodiments, the second receiver is shorter than thefirst receiver along a proximal to distal direction. In someembodiments, the bone screw is a polyaxial screw. In some embodiments,the first rod channel and the second rod channel are at an identicallevel or at two different levels along a proximal to distal direction.In some embodiments, the first connection is integral to the first andsecond receivers, or the first connection is integral to one of thefirst or second receiver but movable relative to the other one of thefirst or second receiver. In some embodiments, the second connection isintegral to the third and fourth receivers, or the connection isintegral to one of the first or second receiver but movable relative tothe other one of the first or second receiver.

In certain embodiments, disclosed herein is a spinal rod, comprising: anelongate body with a non-circular cross section, wherein elongate bodyis configured to be slidely insertable into a spinal rod channel of abone screw receiver, and is configured to be secured within the spinalrod channel of the bone screw receiver by a closure top pressing againstthe elongate body, wherein the non-circular cross section comprises aflat top edge, two flat side edges, and a curved V-shaped bottom edge.In some embodiments, the non-circular cross section comprises curvedcorners. In some embodiments, the spinal rod further comprises aprotrusion extending from an end surface of the elongate body, theprotrusion integral to the elongate body. In some embodiments, theprotrusion comprises a second non-circular cross section that is smallerthan the non-circular cross section of the elongate body. In someembodiments, the second non-circular cross section has a shape that isdifferent from the non-circular cross section of the elongate body. Insome embodiments, the second non-circular cross section comprises ahexagon shape with rounded corners. In some embodiments, the protrusionis configured to be grabbed by a tool for positioning the spinal rodwithin the spinal rod channel. In some embodiments, the resistance totorsion of the elongate body is greater than a spinal rod of circularcross section that fits into the spinal rod channel of the bone screwreceiver. In some embodiments, the flat top edge, the curved V-shapedbottom edge, or both are configured to increase a contacting surface tothe spinal rod channel, a closure top, or both.

In certain embodiments, disclosed herein is a spinal rod, comprising: anelongate body with a non-circular cross section, wherein elongate bodyis configured to be slidely insertable into a spinal rod channel of abone screw receiver, and is configured to be secured within the spinalrod channel of the bone screw receiver by a closure top pressing againstthe elongate body, wherein the non-circular cross section comprises acurved top edge, two curved side edges, and a curved bottom edge. Insome embodiments, the non-circular cross section comprises curvedconnection between the curved edge and either one of the two curved sideedges, and between the curved bottom edge and either one of the twocurved side edges. In some embodiments, the spinal rod further comprisesa protrusion integral to the elongate body, the protrusion extendingfrom an end surface of the elongate body. In some embodiments, theprotrusion comprises a second non-circular cross section that is smallerthan the non-circular cross section of the elongate body. In someembodiments, the second non-circular cross section has a shape that isdifferent from the non-circular cross section of the elongate body. Insome embodiments, the second non-circular cross section comprises ahexagon shape with rounded corners. In some embodiments, the resistanceto torsion of the elongate body is greater than a spinal rod of circularcross section that fits into the spinal rod channel of the bone screwreceiver. In some embodiments, one or more of the curved top edge,curved bottom edge, and two curved side edges are convex.

In certain embodiments, disclosed herein is a spinal rod, comprising: anelongate body with a non-circular cross section, wherein elongate bodyis configured to be slidely insertable into a spinal rod channel of abone screw receiver, and is configured to be secured within the spinalrod channel of the bone screw receiver by a closure top pressing againstthe elongate body, wherein the non-circular cross section comprises aflat top edge and a curved or flat bottom edge. In some embodiments, thenon-circular cross section comprises curved connection between adjacentedges. In some embodiments, the spinal rod further comprises aprotrusion integral to the elongate body, the protrusion extending froman end surface of the elongate body. In some embodiments, the protrusioncomprises a second non-circular cross section that is smaller than thenon-circular cross section of the elongate body. In some embodiments,the second non-circular cross section has a shape that is different fromthe non-circular cross section of the elongate body. In someembodiments, the second non-circular cross section comprises a hexagonshape with rounded corners. In some embodiments, the resistance totorsion of the elongate body is greater than a spinal rod of circularcross section that fits into the spinal rod channel of the bone screwreceiver. In some embodiments, one or more of edges are convex. In someembodiments, the non-circular cross section comprises 10 edges including5 flat edges and 5 convex edges. In some embodiments, the non-circularcross section comprises 12 edges including 6 flat edges and 6 convexedges. In some embodiments, comprises a polygon shape with roundedconnections between two adjacent edges.

In certain embodiments, disclosed herein is a bone screw comprising: abone screw shank comprising a shank head; a dual-head receivercomprising: a first receiver comprising a first base having a cavitytherewithin, the cavity configured to securely receive the shank head; afirst top having an opening to receive a locking element therewithinthereby locking the shank head within the cavity; a second receivercomprising a second base having a rod channel defined between a pair ofarms; and a connection between the first receiver and the secondreceiver.

In some embodiments, the connection is integral to the first and secondreceivers, or the connection is integral to one of the first or secondreceiver but movable relative to the other one of the first or secondreceiver. In some embodiments, a bottom surface of the second base isproximal or distal to a bottom surface of the first base. In someembodiments, a bottom surface of the second base and a bottom surface ofthe first base sit at an identical level along a proximal to distaldirection. In some embodiments, a top surface of the first top is distalto a top surface of the pair of arms of the second receiver. In someembodiments, the first receiver has a lower profile than the secondreceiver along a proximal to distal direction. In some embodiments, thefirst receiver comprises a longitudinal axis extending in a proximal todistal direction, and wherein the connection between the first receiverand the second receiver extends substantially perpendicular to thelongitudinal axis of the first receiver. In some embodiments, the secondreceiver comprises a longitudinal axis extending in a proximal to distaldirection, and wherein the connection between the first receiver and thesecond receiver extends substantially perpendicular to the longitudinalaxis of the second receiver. In some embodiments, the rod channelextends in a first direction, wherein the connection between the firstreceiver and the second receiver extends in a direction that isperpendicular to the first direction, or wherein the connection betweenthe first receiver and the second receiver extends in a direction thatis tilted by an angle from the first direction. In some embodiments, theconnection between the first receiver and the second receiver extendslaterally from an outer surface of one of the pair of arms. In someembodiments, the connection between the first receiver and the secondreceiver extends laterally from an outer surface of the first top, thefirst base, or both of the first receiver. In some embodiments, thesecond receiver comprising a tool engagement groove at an outer surfaceof the second pair of arm at or near a top of the second receiver, andwherein a top edge of the connection between the first receiver and thesecond receiver is distal to the second tool engagement groove. In someembodiments, a bottom surface of the connection between the firstreceiver and the second receiver is proximal to a bottom surface of thefirst base. In some embodiments, the second receiver is configured toreceive a closure top that presses against a rod within the rod channelthereby securing the rod therewithin. In some embodiments, the lockingelement is a lock screw or a second closure top that is smaller in itslongitudinal cross section than the closure top of the second receiver.In some embodiments, the connector is narrower than the first receiver.In some embodiments, second receiver is longer than the first receiveralong a proximal to distal direction. In some embodiments, a maximaldimension in a longitudinal cross section of the first base is smallerthan a maximal dimension in the longitudinal cross section of the secondbase. In some embodiments, the bone screw is a polyaxial screw. In someembodiments, the bone screw is an iliac screw.

In certain embodiments, disclosed herein is a bone screw comprising: abone screw shank comprising a shank head; a receiver comprising a basehaving a cavity therewithin, the cavity configured to accept insertionof the shank head from a bottom of the receiver; a pair of armsextending upwardly from the base; and a rod channel defined between thepair of arms; a load ring configured to be bottom-loaded into thereceiver prior to the insertion of the shank head, wherein the load ringcomprises a pair of legs connected by two concave surfaces at itsproximal side; and a clip ring configured to be inserted into a groovelocated in an inner surface at or near the bottom of the receiver in anopen position when the load ring and the shank head are pushed proximalto a locking position, wherein in the open position, each of the pair oflegs faces an opening of the rod channel and each of the concavesurfaces is aligned with one of the pair of arms. In some embodiments,the bone screw is a polyaxial screw. In some embodiments, the bone screwshank is configured to rotate about a longitudinal axis of the receiverfor about 0 degrees to about 40 degrees before a rod is secured in therod channel. In some embodiments, a maximal polyaxial angulation betweenthe bone screw shank and a longitudinal axis of the receiver is greaterthan 40 degrees. In some embodiments, the load ring is configured to bepushed proximally and rotated away from the locked position duringinsertion of the shank head into the receiver. In some embodiments, theload ring is configured to be pushed distally and rotated to the lockposition subsequent to insertion of the clip ring. In some embodiments,the load ring is configured to rotate about a longitudinal axis of thereceiver for about 90 degrees from the open position to the lockposition. In some embodiments, the shank head is configured to be pusheddistally from the open position to the lock position subsequent toinsertion of the clip ring. In some embodiments, the load ring comprisesan inner surface and a distal portion thereof accommodates a shape of atleast part of the shank head. In some embodiments, the load ringcomprises a top opening allowing access to the shank head from a top ofthe receiver. In some embodiments, the load ring comprises an outergroove between the pair of legs and a bottom portion thereof. In someembodiments, the bottom portion of the load ring is substantiallycylindrical. In some embodiments, a cross section at the bottom portionof the load ring is greater than a cross section at the pair of legsthereof. In some embodiments, the pair of arms comprises a protrusion onan inner surface thereof, the protrusion configured to prevent proximaltranslation of the load ring. In some embodiments, at least part of theshank head extends beyond the distal portion of the inner surface of theload ring when the bone screw shank is rotated from the longitudinalaxis of the receiver. In some embodiments, the bone screw is an iliacscrew or a sacral screw. In some embodiments, the receiver comprises alongitudinal axis extending through a bottom of the base toward a top ofthe pair of arms. In some embodiments, the receiver comprising a toolengagement groove at an outer surface of the pair of arms at or near atop thereof. In some embodiments, the bone screw head comprises amaximal outer diameter that is greater than or equal to an outerdiameter of a closure top that is configured to lock a spinal rod withinthe rod channel.

In certain embodiments, disclosed herein is a method of assembly of abone screw, the method comprising: providing a bone screw shankcomprising a shank head; providing a receiver comprising a base having acavity therewithin, the cavity configured to securely accept insertionof the shank head from a bottom of the receiver; a pair of armsextending upwardly from the base; and a rod channel defined between thepair of arms; providing a load ring configured to be bottom-loaded intothe receiver prior to the insertion of the shank head, wherein the loadring comprises a pair of legs connected by two concave surfaces at itsproximal side; and providing a clip ring configured to be inserted intoa groove located in an inner surface at or near the bottom of thereceiver thereby pushing the load ring and the shank head into an openposition that is proximal to a locking position, wherein in the openposition, each of the pair of legs is at least partly facing an openingof the rod channel and each of the concave surfaces are aligned with thepair of arms.

In certain embodiments, disclosed herein is a method of assembly of abone screw, the method comprising: loading a load ring from a bottom endof a receiver of the bone screw through a cavity thereof prior to theinsertion of the shank head, wherein loading the load ring comprisestwisting the load ring so that each of two opposing concave surfaces ata proximal surface of the load ring is aligned with an upwardlyextending arm of the receiver and pushing the load ring proximally;inserting the shank head into the receiver from the bottom end thereoftill access to a groove in an inner surface of the receiver at or near adistal end thereof is open; inserting a clip ring into the groove in theinner surface of the receiver; pushing the load ring and the shank headdistally; and twisting the load ring in to a locked position so thateach of the two concave surfaces at the top surface of the load ring isaligned with an opening of the rod channel of the receiver, wherein theload ring and the shank head is locked from distal movement.

In certain embodiments, disclosed herein is a bone screw comprising: abone screw shank comprising a shank head; a receiver comprising a basehaving a cavity therewithin, the cavity configured to securely acceptinsertion of the shank head from a top of the receiver; a pair of armsextending upwardly from the base; and a rod channel defined between thepair of arms, wherein the base comprises a recess formed in a bottomsurface thereof, wherein the base and the recess are shaped and sized toallow angulation in a range of about 0 degrees to about 60 degrees in afirst lateral direction and prevent angulation of greater than about 0degrees in a second lateral direction opposite the first lateraldirection; and a load ring configured to be top-loaded into the receiversubsequent to the insertion of the shank head, wherein the load ringcomprises a pair of legs connected by two concave surfaces at itsproximal side. In some embodiments, the receiver comprises a pocket inconnection with the cavity at a distal portion thereof, the pocketconfigured to receive the shank head and allow directional rotationtherewithin. In some embodiments, the pocket comprises a pocket surfacehaving at least part of a spherical surface that accommodates aspherical outer surface of the shank head. In some embodiments, the bonescrew shank is configured to rotate about a transverse axis of thereceiver in the first lateral direction before a rod is secured in therod channel. In some embodiments, a maximal angulation between the bonescrew shank and a longitudinal axis of the receiver is in a range ofabout 0 degrees to about 60 degrees. In some embodiments, a maximalangulation between the bone screw shank and a longitudinal axis of thereceiver is greater than 55 degrees. In some embodiments, when alongitudinal axis of the receiver and a longitudinal axis of the bonescrew shank are aligned, the bone screw is configured to allowderotation movement in the second lateral direction to aid capture of arod. In some embodiments, when a longitudinal axis of the receiver and alongitudinal axis of the bone screw shank are aligned, the receiver isconfigured to provide a hard stop to rotational movement of the bonescrew shank relative to the receiver in the second lateral directionwithout using a rod, a closure top, or any other locking elementexternal to the bone screw. In some embodiments, the load ring comprisesa top opening allowing access to the shank head from a top of thereceiver. In some embodiments, the load ring comprises an inner surfaceand a distal portion of the inner surface accommodating a shape of atleast part of the shank head. In some embodiments, the load ringcomprises a plurality of fingers at its distal end, and wherein theplurality of fingers is configured to impart a frictional fit on theshank head. In some embodiments, the load ring comprises a distal recessat its distal end, the distal recess aligned with the recess of thereceiver. In some embodiments, the distal recess is configured to aidangulation of the bone screw shank in the first lateral direction. Insome embodiments, the angulation of the bone screw shank comprisesmovement in a medial to lateral direction (e.g., along D1) and/ormovement in a cranial to caudal direction (e.g., along L3 axis). In someembodiments, the pair of arms comprises a first protrusion on an innersurface thereof, the first protrusion configured to prevent proximaltranslation of the load ring. In some embodiments, the pair of armscomprises a second protrusion on an inner surface thereof, the secondprotrusion configured to prevent distal translation of the load ring,the second protraction distal to the first protrusion. In someembodiments, at least part of the shank head extends beyond the distalportion of the inner surface of the load ring when the bone screw shankis rotated from the longitudinal axis of the receiver. In someembodiments, the receiver comprises a longitudinal axis extendingthrough a bottom of the base toward a top of the pair of arms. In someembodiments, the receiver comprising a tool engagement groove at anouter surface of the pair of arms at or near a top thereof. In someembodiments, the cavity comprises at least two bottom edges that aresubstantially flat. In some embodiments, each of the at least two bottomedges are connected with a curved edge of the recess. In someembodiments, the shank head comprises a head diameter in a range fromabout 4.0 mm to about 8.0 mm. In some embodiments, the bone screw shankcomprises a length from about 20 mm to about 120 mm. In someembodiments, the bone screw shank is configured to be rotatable about alongitudinal axis of the bone screw shank when the bone screw shank isrotated from a longitudinal axis of the receiver.

In certain embodiments, disclosed herein is a bone screw assemblycomprising: a bone screw shank comprising a shank head; a receivercomprising a base having a cavity therewithin, the cavity configured tosecurely accept insertion of the shank head from a top of the receiver;a pair of arms extending upwardly from the base; and a rod channeldefined between the pair of arms; a compression element configured to betop-loaded into the receiver subsequent to the insertion of the shankhead, wherein the compression element comprises a pair of legs connectedby two concave surfaces at its proximal side, and a lock screwconfigured to be top-loaded into the receiver thereby locking the shankhead relative to the receiver. In some embodiments, the base comprises arecess formed in a bottom surface of the base, wherein the base isshaped and sized to allow angulation in a range of about 0 degrees toabout 60 degrees in a first lateral direction. In some embodiments, thebone screw assembly comprises a favored angle screw that favorsangulation in the first lateral direction. In some embodiments, the baseis shaped and sized to prevent angulation of greater than about 0degrees in a second lateral direction opposite to the first lateraldirection. In some embodiments, the compression element or the receivercomprises a coaxial indicator configured to provide a feedback when alongitudinal axis of the bone screw shank is aligned with a longitudinalaxis of the receiver. In some embodiments, the feedback is a tactilefeedback. In some embodiments, the feedback is prevention of rotation ina second lateral direction. In some embodiments, the compression elementis configured to be loaded with each of the pair of legs facing anopening of the rod channel. In some embodiments, the compression elementis configured to be rotated so that each of the pair of legs faces oneof the pair of arms subsequent to the loading, and then pushed distallyinto a secured position relative to the receiver. In some embodiments,the compression element is configured to be rotated when at a firstlocation, wherein the first location is proximal to a second locationwhere the compression element is in the secured position. In someembodiments, the compression element comprises a barb feature on each ofthe pair of legs, the barb feature configured to interact with acorresponding protrusion on an inner surface of each of the pair of armsthereby allowing distal insertion and preventing proximal movement ofthe compression element relative to the receiver. In some embodiments,the compression element comprises a through bore from a proximal end toa distal end thereof, the through bore configured to allow access of adrive tool to the bone screw shank. In some embodiments, the cavity issized and shaped to prevent pulling off of the shank head from a bottomof the cavity. In some embodiments, the bone screw is a polyaxial screw.In some embodiments, the lock screw is a dual lock screw. In someembodiments, the dual lock screw comprises an outer element that coupleswith an inner surface of the pair of arms, and an inner element that isconfigured to be inserted within the outer element and couples with theouter element. In some embodiments, the outer element comprises ahelical flange threadform that couples with a matching helical flangethreadform on the inner surface of the pair of arms. In someembodiments, the outer element comprises an outer drive feature at ornear a proximal end thereof, the outer drive feature configured toengage a driver tool. In some embodiments, the outer drive featurecomprises a hexalobe at an inner surface of the outer element, thehexalobe extending distally but remaining proximal to a proximal end ofthe inner element. In some embodiments, the outer element comprises aprotrusion located between the hexalobe and a matching inner threadingconfigured to couple to the inner element. In some embodiments, theinner element comprises an inner drive feature, the inner drive featureconfigured to engage a second driver tool. In some embodiments, theinner drive feature comprises a second hexalobe at an inner surface ofthe inner element, the second hexalobe extending from at or near adistal end to at or near a proximal end of the inner element. In someembodiments, the inner element comprises an outer threading that couplesto an inner threading of the outer element. In some embodiments, thedual lock screw is configured to provisionally lock the bone screw headrelative to the receiver prior to inserting a rod in the rod channel ofthe bone screw assembly. In some embodiments, the lock screw is a singlelock screw. In some embodiments, threadform that couples with a matchinghelical flange threadform on the inner surface of the pair of arms. Insome embodiments, the single lock screw comprises a drive featureextending from at or near a proximal end to at or near a distal endthereof, the drive feature configured to engage a driver tool. In someembodiments, the single lock screw is configured to lock the shank headrelative to the receiver when a rod is inserted in the rod channel ofthe bone screw assembly. In some embodiments, the receiver comprises apocket in connection with the cavity at a distal portion thereof, thepocket configured to receive the shank head and allow directional orpolyaxial rotation therewithin. In some embodiments, the pocketcomprises a pocket surface having at least part of a spherical surfacethat accommodates a spherical outer surface of the shank head. In someembodiments, the bone screw shank is configured to rotate about atransverse axis of the receiver in the first lateral direction. In someembodiments, a maximal angulation of the shank head and a longitudinalaxis of the receiver is greater than 55 degrees. In some embodiments, amaximal angulation of the shank head and a longitudinal axis of thereceiver is in a range of about 0 degrees to about 60 degrees. In someembodiments, when a longitudinal axis of the receiver and a longitudinalaxis of the bone screw shank are aligned, the bone screw is configuredto allow derotation movement in the second lateral direction to aid forcapture of a rod within the rod channel prior to derotation. In someembodiments, the compression element comprises an inner surface and adistal portion of the inner surface accommodating a shape of at leastpart of the shank head. In some embodiments, the compression elementcomprises a plurality of fingers at its distal end, and wherein theplurality of fingers is configured to impart a frictional fit on theshank head. In some embodiments, the compression element comprises adistal recess at its distal end, the distal recess aligned with therecess of the receiver when the compression element is in a securedposition. In some embodiments, the distal recess is configured to aidangulation of the bone screw shank in the first lateral direction. Insome embodiments, the angulation of the bone screw shank comprisesmovement in a medial to lateral direction (e.g., along D1) and/ormovement in a cranial to caudal direction (e.g., along L3 axis). In someembodiments, at least part of the shank head extends beyond the distalportion of the inner surface of the compression element when the bonescrew shank is rotated from the longitudinal axis of the receiver. Insome embodiments, the receiver comprises a longitudinal axis extendingthrough a bottom of the base toward a top of the pair of arms. In someembodiments, the receiver comprises a tool engagement groove at an outersurface of the pair of arms at or near a top thereof. In someembodiments, the shank head comprises a head diameter in a range fromabout 4.0 mm to about 8.0 mm. In some embodiments, the bone screw shankcomprises a length from about 20 mm to about 120 mm. In someembodiments, a diameter or a maximal dimension of a cross section of thedual lock screw is in a range of about 5.5 mm to 6.0 mm. In someembodiments, a diameter or a maximal dimension of a cross section of thesingle lock screw is in a range of about 5.5 mm to 6.0 mm. In someembodiments, the rod channel is configured to receive a spinal rodtherewithin, wherein the spinal rod comprises a non-circular crosssection.

Overview

As disclosed herein, “bone screws” are interchangeable with orequivalent to “bone anchors,” “fixation screws,” and “pedicle screws.” A“receiver” of the bone screw is interchangeable with or equivalent to a“tulip” herein. As disclosed herein, a bone screw “assembly” isinterchangeable with or equivalent to a bone screw “construct.”Disclosed herein, in some embodiments, are spinal fixation screws, boneanchors, bone screws, or use of the same.

As disclosed herein, “proximal direction” indicates the direction awayfrom attachment of an element to the subject, while “distal direction”indicates the direction opposite proximal direction and towardattachment of an element to the subject.

As disclosed herein, “integral” to a bone screw may indicate the elementis fixedly attached to the bone screw and does not allow rotational,translational, or perceivable deformable movement relative to the bonescrew.

As disclosed herein, the “load ring” is interchangeable with orequivalent to a “compression element.”

As disclosed herein, L2 and L3 axes are perpendicular to each other, andboth axes are perpendicular to the longitudinal axis, L1, of thereceiver of the bone screw. L3 axis is along the direction of extensionof the rod channel in the receiver.

In some embodiments, the bone screws, spinal rods, rod to rod connectorsor other devices are made of one or more of biocompatible materialsincluding, but not limited to, titanium, stainless steel, cobalt chrome,ceramics and/or thermoplastic materials. In some embodiments, the bonescrews disclosed herein are polyaxial. In some embodiments, the bonescrew may favor angulation in one single direction, e.g., along alateral direction. In some embodiments, the bone screw may favorangulation in a couple of direction that are not parallel to each other.

In some embodiments, the bone screws herein can be either preassembledor modular, e.g. parts of the bone screw may be assembled immediatelypre-operatively or intra-operatively according to the needs of aspecific user. The bone screws herein may be modular for ease ofplacement but can also be made as a preassembled variant.

Bone Screws with Fixed Lateral Rod

Disclosed herein, in some embodiments, are bone screws with a lateralrod. The lateral rod can be fixed or integral to the receiver of thebone screw. Such bone screws disclosed herein may include a bone screwshank comprising a shank head, a receiver having a base having a cavitytherewithin, the cavity configured to securely receive the shank head, apair of arms extending upwardly from the base, a rod channel definedbetween the pair of arms, and a lateral rod integral to or fixedlyattached to the receiver and extends laterally away from the receiver.

FIGS. 1-3 show an exemplary embodiment of the bone screws with lateralrod in a perspective view (FIGS. 1-2) and cross-sectional view (FIG. 3)cutting from D-D′ in FIG. 1. Referring to FIGS. 1-3, in this particularembodiment, the bone screw 100 includes a bone screw shank 300 that canbe securely inserted into a receiver or a tulip 200. The bone screwshank 300 can include a shank head 302 and a shank body 301 that may bethreaded for at least a portion thereof. The shank head can have alarger cross section that the shank body 301. The shank head may bebottom loaded through a cavity 209 located at a base 201 of the receiver200. Alternatively, the shank head may be top-loaded into the receiverduring assembly as disclosed herein in certain cases.

A pair of arms 202 a, 202 b can extend upwardly from the base, the pairof arms 202 a, 202 b may be positioned opposite to each other and may bepositioned to define a rod channel 203 therebetween. The rod channel 203can have two channel openings 203 a, each channel opening determined byan edge of each of the pair of arms. The bone screw receiver includes alongitudinal axis, L1 that extends along the proximal to distaldirection, as shown in FIG. 3. In some embodiments, the longitudinalaxis, L1, of the receiver extends through a distal end or a bottom endof the base toward a proximal end or top end of the pair of arms 202 a,202 b. The bone screw 100 can be a polyaxial screw. Alternatively, thebone screw 100 can be with a favored direction of angulation.

In some embodiments, the bone screw 100 may include a load ring 500, alock ring 600, or both, that may be inserted into the bone screw andfacilitate secured positioning and angulation of the bone screw shank300 to the receiver 200. In some embodiments, the bone screw may includea closure top 700 that can be inserted from a top opening of thereceiver connected to the rod channel 203. The closure top may bepressed against a spinal rod 400 thereby locking the shank head 302relative to the receiver 200. Alternatively, the closure top 700, e.g.,a lock screw, may be used to lock the shank head 302 to the receiverwithout presence of a spinal rod in the rod channel.

Continuing on referring to FIGS. 1-3, in this embodiment, the bone screw100 includes a lateral rod 204 that is fixedly attached to or integralto the receiver 200. The lateral rod can extend substantially in adirection, e.g., L2 axis that is substantially perpendicular to thedirection of extension of the rod channel, e.g., L3 axis.

In some embodiments, the lateral rod may be substantially straight, asshown in FIG. 1. In some embodiments, the lateral rod contains a curvedportion, a bent portion, or a portion that is not substantiallystraight.

In some embodiments, the lateral rod may be extending along the L2 axis,as shown in FIG. 3. L2 axis is substantially parallel to the directionof extension of the rod channel 303, e.g., L3 axis. In some embodiments,the lateral rod may be tilted away from the L2 axis for an acute angle,e.g., about 10-20 degrees, but remain perpendicular to L1 axis. In someembodiments, the lateral rod may be tilted away from the L3 axis for anacute angle, but remain perpendicular to L1 axis. In some embodiments,the direction along which the lateral rod is extending may be in theplane determined by L2 and L3 axes, so that the direction of extensionof the lateral rod remains substantially perpendicular to the L1 axis.

In some embodiments, the direction along which the lateral rod isextending may be in the plane determined by L1 and L2 axes, thus itremains perpendicular to L3 axis instead. In some embodiments, thelateral rod may be tilted away for different acute angle(s) from anyone, two, or three of the L1, L2, and L3 axes dependent on the need ofthe spinal applications.

In some cases, the lateral rod 204 extends laterally from an outersurface 208 of one of the arms, e.g., 202 b, of the receiver 200. Insome embodiments, the outer surface 208 can be partly or entirely on thearm 202 b. The outer surface may be partly or entirely on the base 201.The lateral rod 204 may comprise a cross-sectional shape that isidentical to that of a spinal rod 400 that is configured to be receivedin the rod channel 203 of the bone screw. In this particular embodiment,the lateral rod 204 comprises a substantially cylindrical shape. In thisembodiment, the lateral rod 204 includes a circular cross sectionperpendicular to L2. In some embodiments, the lateral rod may comprise anon-circular cross section including but not limited to the non-circularcross sections disclosed herein, perpendicular to L2. The lateral rodmay include a length that can be customized. For example, the lateralrod may include a length in a range of about 1 cm to about 20 cm.

In some embodiments, the lateral rod 204 includes a size that can bereceived in a rod to rod connector 800. FIGS. 4-5 show an exemplaryembodiment of two bone screws 100 that are connected together into anassembly 900 with a spinal rod 400 extending in a first direction, L3axis, through the rod channel of each of the bone screws. FIG. 4 shows aperspective view of the assembly 800, and FIG. 5 shows a top view of theassembly. In this embodiment, a rod to rod connector 800 can securelyreceive the first lateral rod 204 in a first bore 801 a and the secondlateral rod in a second bore 801 b of the rod to rod connector 800. Thefirst bore and the second bore of the rod to rod connector can besubstantially parallel to each other.

In some embodiments, the first bone screw is anchored to a firstvertebral bone, and the second bone screw is anchored to a secondvertebral bone. In some embodiments, the first bone screw or the secondbone screw is a poly-axial screw. The rod to rod connector 800 cancomprises a first opening 803 at a top thereof, the first openingconnected to the first bore and the first opening is configured toreceive a closure top 802 that can press against the first lateral rodthereby securing the first lateral rod to the rod to rod connector 800.Similarly, the rod to rod connector can have a second opening 803 at atop thereof, the second opening connected to the second bore 801 b. Insome embodiments, the rod to rod connector may include more than twobores that can be used to include more than two lateral rods of bonescrews or a combination of lateral rod(s) 204 of bone screws andconventional spinal rods 400.

In some embodiments, the receiver 200 includes a tool engagement groove205 at an outer surface of the pair of arms 202 a, 202 b at or near atop end thereof, and wherein a top edge of the lateral rod 207 is distalto the tool engagement groove. In some embodiments, a bottom edge 206 ofthe lateral rod is proximal to a distal end 201 c of the base.

In some embodiments, the bone screws 100 disclosed herein have aprotruding rod portion or a lateral rod 204 off the tulip or receiver200 on the medial or lateral side to allow for connection with otherdevices, e.g., with existing rod to rod connectors 800. In someembodiments, two bone screws placed adjacent to each other can becoupled using a “H” style rod to rod connector, e.g., in FIGS. 4-5. Forexample, the two bone screws may be anchored on two different vertebraeon adjacent vertebral levels. This may advantageously allow for the twobone screws on each side of two adjacent fixated levels to be coupled,making the segment a solid construct, thereby minimizing or eliminatingrelative movements between the two levels along the cranial to caudaldirection (e.g., along L3 axis) and/or along other directions. Once thelateral rods 204 between the adjacent bone screws are coupled using arod-rod connector 800, the tulip or receiver 200 of the bone screws canstill accept a spinal rod 400 in order to be tied into the longconstruct. Once the desired vertebral levels, for example levels aboveand below a pedicle subtraction osteotomy (PSO) or unstable junctionbetween adjacent levels caused by osteotomies, revision, corpectomy intrauma or tumor, or resection, are secured to one another using theimplant and rod to rod connectors, then a spinal rod 400 can be placedbilaterally and used as template to further control or assist therelative kyphosis or lordosis between the two levels without causingrotation or slipping between the two unstable levels in order to preventdamage to the spinal cord/caudal equina. The two converging bone screwsand connectors together may create a stronger segment across theunstable bodies to allow for correction and safety during sagittal andcorona alignment during correction of a complex deformity.

In some embodiments, this bone screw design advantageously allows forthe coupling of two adjacent level pedicle screws on the same side of aconstruct using rod-rod connections, e.g., left or right side of theconstruct. The implant can allow two levels to be coupled to minimize oreliminate vertical translation, e.g., along L3 axis, along caudal tocranial direction but may provide freedom in varying lordosis kyphosisas well as some degree of medial or lateral angulation. The coupled bonescrews can still be connected to other bone screws or bone screwassemblies using connection to the same spinal rod 400. The bone screws200 or bone screw assemblies 900 may give flexibility in buildingconstructs for complex deformity and trauma applications whereconnection(s) to a spinal rod may be needed. The implant may take theplace of using multiple satellite rods or rod-rod connectors along withpedicle screws and allow the ability to tie-in a PSO level to the entireimplant construct or a spinal rod.

Dual-Head Screw Connectors

Disclosed herein, in some embodiments are bone screws with a dual-head.Referring to FIGS. 7-9, in a particular embodiment, the bone screw 100includes a single bone screw shank 300 having a shank head 302 and ashank body 301. The dual-head receiver 200 may include a first receiver200 with a first base 201 having a cavity 209 therewithin. The cavitycan be configured to securely receive the shank head 302. The firstreceiver can include a first pair of arms 202 a, 202 b extendingupwardly from the first base. The bone screw may include a first rodchannel 203 defined between the first pair of arms. The bone screw 100may also include a second receiver 230 with a second base 231 having asecond rod channel 233 defined between a second pair of arms 232 a, 232b. There can be a connection 220 between the first receiver 200 and thesecond receiver 230. The connection can be integral to the first andsecond receivers or movable relative to the first or the secondreceiver. In some embodiments, the first rod channel 203 extends in afirst direction, L3, and the second rod channel 233 extends in a seconddirection, L2, substantially perpendicular to the first direction. Insome embodiments, at least part of the first pair of arms 202 a, 202 bface an opening of the second channel 233 while at least part of thesecond pair of arms 232 a, 232 b face an opening of the first channel203. In some cases, a bottom 231 c of the second base is proximal to abottom surface of the first base 201 c.

Continuing referring to FIGS. 7-9, in the same embodiment, the firstreceiver 200 comprises a longitudinal axis L1 extending in a proximal todistal direction, and wherein the connection 220 between the firstreceiver and the second receiver extends in a different direction alongL2 axis. The L2 axis may be substantially perpendicular to thelongitudinal axis of the first receiver, L1. The connection 220 betweenthe first receiver and the second receiver can extend laterally from anouter surface of one of the first pair of arms 202 b. In the sameembodiment, the connection between the first receiver and the secondreceiver may extend laterally from an outer surface of an opening of thesecond rod channel 233 b. In some embodiments, the first rod channel 203and the second rod channel 233 comprise an identical size, shape, orboth. In alternative embodiments, the first rod channel and the secondrod channel have a different size or shape.

In some embodiments, the connection 220 may be substantially straightand extending along L2 axis. L2 axis can be substantially to thedirection of extension of one of the rod channels, 203, 233, e.g., L3.In some embodiments, the connection 220 may not be substantiallystraight. For example, the connection may include a curved portion or abend portion. Referring to FIGS. 39A-39B, in a particular embodiment,the connection 220 may include a portion that is substantially straightand extending along L2 axis, 220 a. In the same embodiment, theconnection 220 may also include a curved portion, 220 b, connecting thestraight portion and the second receiver 230.

In some embodiments, the connection 220 may be extending along the L2axis. In some embodiments, the connection may be extending in adirection that is tilted from L2 axis. The connection may also beconfigured to include a different thickness along L2 axis so that thefirst rod channel 203 and the second rod channel 233 may be at twodifferent levels along the L1 axis. In this particular case, the secondrod channel is proximal to the first rod channel as shown in FIG. 39A.

In some embodiments, the first receiver 200 has a first tool engagementgroove 205 at an outer surface of the first pair of arms at or near atop surface thereof, and wherein a top edge of the connection 217between the first receiver and the second receiver is distal to thefirst tool engagement groove 205. The second receiver 230 can include asecond tool engagement groove 235 at an outer surface of the second pairof arms at or near a top surface thereof, and wherein a top edge 217 ofthe connection between the first receiver and the second receiver isdistal to the second tool engagement groove 235.

In some embodiments, a bottom surface 218 of the connection 220 betweenthe first receiver and the second receiver is proximal to a bottom ofthe first base 201 c.

In some embodiments, the first receiver is configured to receive a firstclosure top 700 that presses against a first rod 400 within the firstrod channel 203 thereby securing the first rod 400 therewithin. Thesecond receiver 230 can be configured to receive a second closure top700 that presses against a second rod within the second rod channel 233thereby securing the second rod therewithin.

In the same embodiments, the first receiver 200 may comprise a U-shapeopening 203 b defined by at least part of an edge of each of the firstpair of arms 202 a, 202 b. Similarly, the second receiver 230 comprisesa U-shape opening 233 b defined by at least part of an edge of each ofthe second pair of arms. In some embodiments, the connector 220 isnarrower than the first receiver 200 along the L3 axis. The secondreceiver 230 is shorter than the first receiver 200 along a proximal todistal direction, L1. Referring to FIG. 8, in the same embodiment, thesecond rod channel 233 extends laterally beyond an edge of each of thesecond pair of arms 232 a, 232 b. In this specific embodiment, thesecond rod channel 233 extends laterally beyond a lateral edge of thesecond receiver 230.

In some embodiments, the bone screw 100 is polyaxial. In someembodiments, the bone screw may favor angulation in one or moredirections, e.g., along a lateral direction.

In some embodiments, the second receiver 230 may or may not include acavity that is configured to receive a bone screw shank therein.

As can been seen in FIG. 8, the second rod channel 233 comprises ahalf-moon opening at a lateral edge of the second receiver 230.

In some embodiments, the dual head bone screw 100 may be connected toanother bone screw 200, either conventional or dual head screw, to forma bone screw construct or assembly. Referring to FIGS. 10-11, in aparticular embodiment, two dual head bone screw 100 are connected usinga spinal rod 400, into a bone screw assembly 900. In this embodiment,the bone screw assembly may have a first bone screw 100 as shown inFIGS. 7-9. This first bone screw may include a first dual-head receiver200. In addition to the first bone screw, the assembly 900 may alsoinclude a second bone screw 100 as shown in FIGS. 7-9, and similar tothe first bone screw. The first bone screw and the second bone screw maybe anchored to a vertebral body 910 at an identical level but at twodifferent lateral sides of the medial line of the vertebra. FIG. 10shows a perspective view of an exemplary embodiment of the bone screwassembly 900, and FIG. 11 shows a cross-sectional view of the exemplaryembodiment of the bone screw assembly 900. The spinal rod 400 connectingthe two dual head bone screws 100 may be extending substantiallylateral, along L2 axis. In some embodiments, the spinal rod may have alength along L2 that can be customized to fit in the rod channel 233 ofeach of the both bone screws 100.

In some cases, the dual head screw 100, when implanted in the patient,has one rod channel that can be running vertical and in the planedetermined by cranial to caudal (e.g., along L3 axis) and left to rightdirections while the other is running orthogonal to the first rod slot,e.g., horizontal, as shown in FIGS. 10-11. This can allow a horizontalrod 400 to be placed across a vertebral body or segment between the twobilateral dual headed screws 100. Once the horizontal rod 400 is lockedbetween the two screws 100, the shank heads 302 of the screws can stillrotate in the cranial to caudal direction.

In some embodiments, the bone screw assembly 900 may run a diagonalcrossing rod across two adjacent vertebral levels to secure torsionalresistance but the goal may be to connect screws at the same level. Oncethe levels above and below the PSO or unstable junction caused byosteotomies, revision, resection, or a combination thereof are securedwith crossing rods, then a rod can be placed bilaterally and used astemplate to control or assist compression of the two levels togetherwithout causing rotation or slipping between the two unstable levels inorder to prevent damage to the spinal cord/caudal equina. The twoconverging screws and a rod spanning the median distance between themmay create a triangle that is rigid to torsion and medial/lateral splaybut allows for rotation in the cranial to caudal direction (e.g., alongL3 axis).

The dual headed screw may allow for dual rod connections from one placedpedicle screw shank in order to give improved flexibility in buildingconstructs for complex deformity and trauma applications whereconnection to both the longitudinal rod, e.g., along L3 axis, andlateral rod, e.g., along L2 axis, may be needed. The single dual headconnector may take the place of using multiple rod to rod connectorsalong with pedicle screws and allows the ability to tie-in a PSO levelto the entire construct or longitudinal rod.

In some embodiments, the dual head bone screws disclosed herein mayinclude two rod channels that are substantially parallel to each other.

Referring to FIGS. 12-14, in a particular embodiment, the dual head bonescrew 100 includes similar structural elements to the bone screw shownin FIGS. 7-9, except that the rod channels are substantially parallel toeach other.

In this particular embodiment, the bone screw 100 comprises a bone screwshank 300 comprising a shank head 302, a dual-head receiver 200 having afirst receiver 210 comprising a first base 201 having a cavity 209therewithin, a first pair of arms 202 a, 202 b extending upwardly fromthe first base 201, a first rod channel 203 defined between the firstpair of arms. The bone screw also may include a second receiver 230comprising a second base 231 having a second rod channel 233 definedbetween a second pair of arms 232 a, 232 b; and a connection 220 betweenthe first receiver and the second receiver, the connection integral tothe first and second receivers, or movable relative to one or both ofthe receivers. In some embodiments, the connection 220 may be formed byone of the first pair of arms 201 b and one of the second pair of arms232 a. In this particular embodiment, the first rod channel 203 extendsin a first direction, e.g., along L3 axis, and the second rod channelextends in a second direction substantially parallel to the firstdirection, e.g., also along L3 axis. In the same embodiment, the firstpair of arms 202 a, 202 b, faces the second pair of arms 232 a, 232 b.

In some embodiments, the first and second rod channels are extending intwo directions that are tilted by an acute angle from each other. As anexample, the first channel can be extending along L3 axis, and thesecond rod channel extending in a direction that is tilted by 15 degreesfrom L3 axis, but both directions are still perpendicular to L1 axis. Insome embodiments, one or both of the rod channels, 203 and 233 mayextend in a direction that is tilted from one or more of the L1, L2, L3axes, and the three axes shown in FIGS. 12-13.

In some embodiments, the connection 220 may be substantially straightand extending in a direction perpendicular to L3, e.g., along L2 axis asin FIGS. 11-12. In some embodiments, the connection 220 may not besubstantially straight. For example, the connection may include a curvedportion or a bend portion. In some embodiments, the connection 220 maybe extending along the L2 axis. In some embodiments, the connection maybe extending in a direction that is tilted from L2 axis or L3 axis,e.g., L3′ axis. Referring to FIGS. 40A-40B, the connection 220 may beextending in a direction that is within a plane determined by L3 and L2axes, thus it may remain perpendicular to L1. The angle between the L3and L3′ axes may be acute, for example, it may be within a range fromabout 5 degrees to about 40 degrees. In some embodiments, the anglebetween the L3 and L3′ axes may be within a range of about 15 degrees toabout 30 degrees. In some embodiments, the connection may be extendingin a direction that is tilted from one or more of the L1, L2, and L3axes.

The connection may also be configured to include a different thicknessat different portions thereof, the thickness can be along L1 axis. Thethickness of the connection may not be uniform so that the first rodchannel 203 and the second rod channel 233 may be at two differentlevels along the L1 axis. In this particular case, the second rodchannel is positioned proximal to the first rod channel as shown in FIG.39A.

In some embodiments, a bottom surface 231 c of the second base isproximal to a bottom surface of the first base 201 c. In thisembodiment, the connection 220 between the first receiver and the secondreceiver extends substantially perpendicular to the longitudinal axis,L1, of the first receiver or the second receiver. In some embodiment,the connection 220 extends along L2. The connection 220 between thefirst receiver and the second receiver may extend laterally from anouter surface of one of the first pair of arms 201 b on one side andfrom an outer surface of one of the second pair of arms 232 a on theother side. In some embodiments, the connection may extend laterallyfrom an outer surface of the first base 201 to an outer surface of thesecond base 231. The two rod channels, 203, 233 can comprise anidentical size or shape. A bottom surface of the connection 221 c can beproximal to a bottom surface 201 c of the first base, a bottom surfaceof the second base 231 c, or both. The first receiver 210 may include aproximal or top opening that is configured to receive a first closuretop 700 that presses against a first rod 400 within the first rodchannel 203 thereby securing the first rod therewithin, and the secondreceiver may have a second proximal opening that is configured toreceive a second closure top 700 that presses against a second rod 400within the second rod channel 233 thereby securing the second rodtherewithin. In some embodiments, the first receiver 210 comprises aU-shape opening 203 a defined by at least part of an edge of each of thefirst pair of arms 202 a, 202 b, and the second receiver 230 comprises aU-shape opening 233 b defined by at least part of an edge of each of thesecond pair of arms 232 a, 232 b. The second receiver can be shorterthan the first receiver along a proximal to distal direction, e.g., L1axis. In some embodiments, the first rod channel and the second rodchannel are at an identical level along a proximal to distal direction,L1. The bone screws can be polyaxial or with favored angulation in oneor more directions.

In some embodiments, the dual head bone screw 100 with parallel rodchannels may be connected with another bone screw, e.g., a dual headbone screw, any other bone screw disclosed herein, or any traditionalbone screw, to form a bone screw assembly.

In some embodiments, the dual head bone screw 100 may include two rodchannels 203, 233 that are not parallel to each other. In someembodiments, the dual head bone screw may include a second rod channel233 that may be translatable or rotatable relative to the first rodchannel 203 in different directions. As a non-limiting example, theconnection between the first and the second receiver can be rotatablelyconnected to the first receiver and can be rotated so that the secondrod channel may become side-loading as shown in FIG. 14. In thisparticular embodiment, the first receiver and the second receiver arenot fixedly connected or integral to each other, and include aconnection that can be rotatable about L2 axis and/or translatable alongL2 axis. The second receiver 230 can be rotated for loading a spinal rodfrom its side. The second receiver can include a rod channel that isparallel to the first rod channel before any movement, and may still beparallel to the first rod channel after movement as shown in FIG. 14.

Referring to FIGS. 19A-19D, in some embodiments, the connection 220 maybe integral to one of the first receiver 210 and the second receiver230, but rotatable and/or translatable to the other one of the first andsecond receivers. In these particular embodiments, the connection may beintegral to the first receiver 210, but the second receiver is movablerelative to the connection 220 and the first receiver. As a result, thesecond receiver 230 may be rotatable about the L2 axis from the positionshown in FIG. 12, to a rotated position as shown in FIG. 19C. Forinstances, the second receiver 230 can be rotated about the L1 axis fromthe position shown in FIG. 12 to the position shown in FIG. 19D. FIG.19B shows a side view of the dual-head bone screw in FIG. 19C where thesecond receiver is rotated away for an acute angle from L1 axis. In someembodiments, the connection 220 may also enable translation of thesecond receiver relative to the first receiver to optimize the distancebetween the first and second rod channels.

In some embodiments, one of the first and second rod channels 203, 233,may be rotated one or more of L1, L2, and L3 axes. As an example, thefirst channel can be extending along L3 axis, and the second rod channelextending in a direction that is tilted by 15 degrees from L3 axis, butboth directions are still perpendicular to L1 axis. In some embodiments,one or both of the rod channels, 203 and 233 may extend in a directionthat is tilted from one or more of the L1, L2, L3 axes, and the threeaxes are shown in FIGS. 19A-19D.

In some embodiments, the dual head screws with parallel rod channels canbe advantageously used to allow for a medial and lateral rod to beplaced next to one another in a construct or assembly having multiplerods, e.g., three or four rods. In some embodiments, the dual headscrews with parallel rod channels may advantageously provide animprovement over traditional rod to rod connectors and pedicle screwswhere one head is a pedicle screw with an open or closed tulip orreceiver to capture one rod and the other head medially or laterallyaway from the first head is a tulip that can be either open, closed, orside loading. The two rod connections, or the two bone screw heads caneither be fixed to one another or translatable, or rotatable relative toone another. The dual head bone screws disclosed herein and theirassemblies may replace the traditional need to have both a pediclescrews and a rod to rod connector at each level when placing satelliterods.

Spinal Rods

Disclosed herein, in some embodiments, are spinal rods that fit into rodchannels of the bone screws disclosed herein, connectors, or any otherexisting fixation devices. The spinal rods herein may include anelongate body with a non-circular cross section.

Referring to FIGS. 15A-15H, in some embodiments, the spinal rod 400 mayinclude an elongate body 401 with a non-circular cross section 402 thatis perpendicular to the elongate body. The cross section in FIG. 15B canbe obtained by cutting along A-A′ as shown in FIG. 15A. The crosssection in FIG. 15D can be obtained by cutting along B-B′ as shown inFIG. 15C. The spinal rods 400 disclosed herein may be shaped and sizedso that they can be inserted into a spinal rod channel of a bone screwreceiver, e.g., 200, a rod to rod connector 800, or other spinalfixation devices. In some embodiments, the spinal rods disclosed hereinare configured to be secured within the spinal rod channel 203 or a bore801 a, 801 b, by a closure top 700 pressing against the elongate body.

In some embodiments, the non-circular cross section 401 may includedifferent shapes and/or sizes. FIGS. 15B, 15D, 15F, and 15H showexemplary embodiments of the non-circular cross sections. As shown inFIG. 15B, the cross section 401 may comprise a flat top edge 404, twoflat side edges 405, and a curved V-shaped bottom edge 406. The crosssection may also include curved corners. The curved corners may connecttwo adjacent edges of the cross section.

The spinal rod may include a protrusion 403 extending from an endsurface of the elongate body 401, the protrusion integral to theelongate body. The protrusion can have a second non-circular crosssection that is smaller than the non-circular cross section of theelongate body. The second non-circular cross section may or may not havea shape that is different from the non-circular cross section of theelongate body. Referring to FIG. 15A, in a particular embodiment, thesecond non-circular cross section comprises a hexagon shape with roundedcorners. The protrusion may be configured to be to provide a holdingmeans for a surgeon or a maneuver tool so that the positioning of thespinal rod in the rod channel can be adjusted.

In some embodiments, the spinal rods disclosed herein can be used fordifferent functions during a spinal procedure. For example, the spinalrods herein can be used as a working rod or a final locking rod.

In some embodiments, the cross section of the spinal rods disclosedherein are optimized to fit within the bone screw receiver 200 disclosedherein and has rounds on all corners to aid with manufacturing and toprevent stress concentrations. The spinal rod may resist torsion withinthe receiver of the pedicle screw. The spinal rods with a non-circularcross section may provide resistance to torsion that is greater thanthat of a spinal rod of circular cross section that fits into spinal rodchannel of the bone screw receiver. The shape and/or size of the crosssection may help the rod to self-center in the load ring of the receiverwhen tightened down due to the wedge/V-shape and flat on top. The rod ayhave a better lockdown interface with a set screw because now it has aflat to flat connection that maximizes the surface area in contact toincrease rod resistance to slippage.

In some embodiments, these spinal rods disclosed herein can beadvantageously used as the contra-lateral rods following a rod rolltechnique, where straightness of the rod in the sagittal plane needs tobe maintained. In some embodiments, the spinal rods may be bent to whatthe corrected spine should be so that after an initial rod rolltechnique using a circular rod, one rod can be placed on thecontra-lateral side and then locked down, then the other can replace thelateral circular rod. In some embodiments, the spinal rods herein can beused as an alternative to a global distractor where instead of droppingin satellite rods, this is a hop-scot technique, where a non-implantablerod can be used for the correction then drop in the opposing rod to lockdown correction and then replace the working rod with a final lockingrod. The working rod in this technique could be reused just for rigidityin correction but replaced with smaller profile rods out of titanium fora less rigid final construct to help prevent screw pullout.

In some embodiments, the spinal rods with a non-circular cross sectionherein can be advantageously used as deformity rods in order to increasestrength and rigidity relative to circular cross section rods but withan overall lower profile of rods with equivalent polar moment ofinertia. These rods may have flat edge(s) on the lateral sides to aidwith rotational stiffness and allow rotational control over the rodthrough alignment with the walls of the rod slot feature on the screw.The rod may have a flat edge on the posterior side to maximize oroptimize surface contact with the set screw during lock down. Theanterior portion of the rod may a wedge shape to self-center in thepedicle screw when being locked down and further drive lateral alignmentwith the tulip of the pedicle screw. In some embodiments, the spinalrods disclosed herein with non-circular cross section are configured toprovide a contact surface that is greater than that provided by atraditional spinal rod, either on the proximal side or distal side ofthe rod.

Continuing referring to FIGS. 15A-15B, the cross section are shaped likea shield, horizontally flat on the top, vertically flat on the sideswith a rounded V-shape on the bottom. Referring to FIGS. 15C-15D, in oneembodiment, the non-circular cross section comprises a curved top edge,two curved side edges, and a curved bottom edge. Referring to FIGS.15E-15H, wherein the non-circular cross section comprises a flat topedge and a curved or flat bottom edge.

In some embodiments, the spinal rod may include a top surface, a bottomsurface, or both that increases the contacting surface with the rodchannel or a closure top. In some embodiments, the cross section of thespinal rod may be a polygon shape but the connecting point between twoadjacent edges is rounded.

In some embodiments, the non-circular cross section may comprise curvedconnection(s) or curved corner(s) between two adjacent edges. Forexample, between the curved top edge and either one of the two curvedside edges, and/or between the curved bottom edge and either one of thetwo curved side edges. In some embodiments, one or more of the curvedtop edge, curved bottom edge, and two curved side edges are convex. Insome embodiments, the spinal rods disclosed herein may include a crosssection with 4 edges, as shown in FIGS. 15B and 15D. In someembodiments, the spinal rods herein may include a cross section with 6edges with each pair of adjacent edges connected with a rounded corner,as shown in FIG. 15F. In some embodiments, the spinal rods herein mayinclude a cross section with 12 edges and rounded corners, as shown inFIG. 15H.

In some embodiments, the spinal rods with non-circular cross section maybe used to advantageously provide more strength than conventionalfixation rod with a circular cross section without making a higherprofile since this profile of the spinal rod may drive the overallheight of the tulip or receiver. In some embodiments, the spinal rod maybe more resistant to torsion and may create a more rigid engagementwithin the receiver of the pedicle screw than traditional spinal rodswith circular cross section.

In some embodiments, the spinal rod herein includes an increasedcross-sectional width than the traditional rods with circular crosssection. This increased width may help eliminate the ability to roll therod within a pedicle screw, resist torsion and allow greater axialrotation correction operatively. In some embodiments, the size and shapeof the spinal rods disclosed herein may help maximize the connectionbetween the rod and the receiver to make the combination as rigid aspossible, maximize the polar moment of inertia relative to height,maximize the mating surface between the set screw and rod to increaselockdown strength and prevent slippage.

Moment of inertia, I, can be considered as stiffness relative to crosssection. Referring to FIGS. 16A-16D, polar moment of inertia fortorsion, J, with different cross sections can be calculated differently.

Iliac Screws

In some embodiments, disclosed herein are bone screws, e.g., iliacscrews that do not require insertion of a rod to lock the shank relativeto the receiver. Instead, the receiver or tulip may have a low profileand can lock to the shank via a lock screw or other closure tops. Astrut or rod off the lateral side of the tulip allows for connection ofa rod to rod connector or has a tulip/rod slot to connect directly to aspinal rod of the construct. In some embodiments, the bone screws hereincan be either preassembled or modular. In some embodiments, the rodsherein can be either a straight or angled rod as the strut or atulip/rod slot.

The bone screws disclosed herein may be an alternative implant to theexisting open or closed iliac screws which can be placed on the ilium,sacrum, or sacroiliac region and require either a sharp bend in thelongitudinal rod to join with screws at superior levels or a secondaryhorizontal rod or offset tulip connector. The bone screws herein may beused in a streamlined offering to reduce the number of differentconnectors and overall bulk of the construct while making a more rigidconstruct by reducing the number of connection points/places to fail.The bone screws herein may be modular for ease of placement but can alsobe made as a preassembled variant.

Referring to FIGS. 17A, 17B, and 18, in a particular embodiment, thebone screw 100 includes a bone screw shank 300 comprising a shank head302, a dual-head receiver 200 having a first receiver 210 comprising afirst base 201 having a cavity 209 therewithin, a first top having a topopening 219 to receive a locking element 701 therewithin thereby lockingthe shank head 302 within the cavity, without insertion of a spinal rodtherewithin the receiver. The bone screw also includes a second receiver230 comprising a second base 231 having a rod channel 233 definedbetween a pair of arms 232 a, 232 b; and a connection 220 between thefirst receiver 210 and the second receiver 230, the connection integralto the first and second receivers.

In some embodiments, a bottom surface 231 c of the second base 231 isproximal or distal to a bottom surface 201 c of the first base 201 c. Asshown in FIG. 18, the bottom surface of the second base 231 c and abottom surface of the first base 201 c sit at an identical level along aproximal to distal direction, L1. In some embodiments, a top surface 201d of the first top is distal to a top surface 231 d of the pair of armsof the second receiver 230, along L1 axis. In some embodiments, thefirst receiver 210 has a lower profile than the second receiver 230along a proximal to distal direction, L1.

Continue to refer to FIGS. 17A, 17B, and 18, in this embodiment, theconnection 220 between the first receiver and the second receiverextends along an axis that is substantially perpendicular to thelongitudinal axis of the second receiver, L1. The L2 axis can also besubstantially perpendicular to the L3 axis in which the spinal rodchannel 233 is extending. The connection between the first receiver andthe second receiver may extend laterally from an outer surface of onearm 231 b of the pair of arms, along L2. On the opposite side, theconnection between the first receiver and the second receiver may extendlaterally from an outer surface of the first top, the first base 201, orboth of the first receiver 210. A bottom surface of the connection 221 cbetween the first receiver and the second receiver is proximal to abottom surface of the first base 201 c and/or a bottom surface of thesecond base 231 c. The connector 220 is narrower than the first receiverand/or the second receiver in a direction L3, which is perpendicular toL1 and L2 axes as can be seen in FIGS. 17B and 18.

In some embodiments, the connection 220 may be integral to or fixed toboth receivers. In some embodiments, the connection 220 may be integralto one of the first receiver 210 and the second receiver 230, butrotatable and/or translatable to the other one of the first and secondreceivers. As a result, one of the receiver, e.g., the second receiver230 may be rotatable about the L1 or L3 axis. In some embodiments, theconnection 220 may also enable translation of the second receiverrelative to the first receiver to optimize the distance between thefirst and second rod channels.

In some embodiments, the connection 220 may be substantially straight,as shown in FIGS. 17A-17B. In some embodiments, the connection containsa curved portion, a bent portion, or a portion that is not substantiallystraight.

In some embodiments, the connection 220 may be extending along the L2axis, as shown in FIG. 17B. In some embodiments, the connection 220 maybe tilted away from the L2 axis for an acute angle, e.g., about 10-20degrees. In some embodiments, the connection 220 may be tilted away fromthe L3 axis for an acute angle. In some embodiments, the direction alongwhich the connection is extending may in the plane determined by L2 andL3 axes, so that the direction of extension of the lateral rod remainssubstantially perpendicular to the L1 axis. In some embodiments, thedirection along which the connection is extending may be in the planedetermined by L1 and L2 axes, thus it remains perpendicular to L3 axisinstead. In some embodiments, the lateral rod may be tilted away fordifferent acute angle(s) from any one, two, or three of the L1, L2, andL3 axes dependent on the need of the spinal applications.

In some embodiments, the top opening 219 of the first receiver issmaller in its longitudinal cross section than the top opening 239 ofthe second receiver. In some embodiments, a maximal dimension in alongitudinal cross section of the first base is smaller than a maximaldimension in the longitudinal cross section of the second base. In someembodiments second receiver is longer than the first receiver along aproximal to distal direction, L1.

In some embodiments, the bone screw 100 is a polyaxial screw. In someembodiments, the bone screw is an iliac screw. In some embodiments, thebone screw is configured to be inserted in the ilium, sacrum, orsacroiliac region and require either a sharp bend in the longitudinalrod to join with screws at superior levels or a secondary horizontal rodor offset tulip connector. An exemplary embodiment of the bone screw(s)inserted in a subject is shown in FIG. 19.

Lumbo-Sacral-Pelvic Bone Screws

The bone screws disclosed herein may be pedicle screw that can be bottomloaded and provide more than 40 degrees of polyaxial angulation. Suchpolyaxial angulation may even be achieved with an oversized shank head.The oversized shank head may include a maximal outer diameter that isgreater than or equal to the outer diameter of a closure top that fitsin the receiver. In some embodiments, the oversized head includes adiameter of greater than 8.5 mm. In some embodiments, the oversized headincludes a diameter of greater than 9 mm or 9.5 mm. In some embodiments,the oversized head includes a diameter of greater than 9.8 mm or 9.9 mm.The receiver may be a modified version of existing pedicle screws whichmay retain some or even all of the proximal engagement features forinstrument compatibility but may have a unique distal geometry. Thescrew can be assembled uniquely in that the load ring may be bottomloaded and may be twisted and pushed proximally into the tulip to allowthe shank head to be bottom loaded with enough space for a clip ring ora lock ring to be assembled below the shank head. Once the clip ring isassembled the shank and load ring may be forced distally and then theload ring is rotated into placed to lock the bone screw. This design maybe intended for large diameter screws used in the iliac and sacrum wherea marginal increase in tulip height can be tolerated for increasedangulation.

FIGS. 20, 21A-21B, 22A-22I, and 23A-23C show exemplary embodiments ofsuch bone screws 100. The bone screws 100 may include a bone screw shank300 comprising a shank head 302, a receiver 200 having a base 201 with acavity 209 therewithin, the cavity configured to securely acceptinsertion of the shank head from a top of the receiver. The bone screwmay include a pair of arms 202 a, 202 b extending upwardly from the base201, and a rod channel 203 defined between the pair of arms. The bonescrew may include a load ring 500 that can be bottom-loaded into thereceiver prior to the insertion of the shank head 302, wherein the loadring comprises a pair of legs 501 a, 501 b connected by two concavesurfaces 502 a, 502 b at its proximal side, as shown in FIGS. 22A-22B.The bone screw may also include a clip ring 600 that can be insertedinto a groove 214 located in an inner surface at or near the bottom ofthe receiver in an open position when the load ring and the shank headare pushed proximal to a locking position. An exemplary embodiment ofthe locking position is shown in different views in FIGS. 23A (topview), 23B (cross section view cutting along F-F′ in FIG. 23A), and 23C(cross section view rotated from FIG. 23B). An exemplary embodiment ofthe open position is shown in FIGS. 22F-22I. In the open position, eachof the pair of legs 501 a, 501 b, faces an opening of the rod channel203 and each of the concave surfaces 502 a, 502 b is aligned with one ofthe pair of arms. When in an open position, the top end of the legs 501a, 501 b of the load ring is at a first location that is proximal to thesecond location in a locked position, as shown in FIGS. 221 and 23B.

In some embodiments, the bone screw is a polyaxial screw. The bone screwshank may rotate from a longitudinal axis of the receiver, L1, for about0 degrees to about 40 degrees, as shown in FIG. 21B. In someembodiments, the rotation may be before a rod is secured in the rodchannel 203. A maximal polyaxial angulation between the bone screwshank, L4, and a longitudinal axis of the receiver, L1, can be greaterthan 40 degrees. The load ring 500 may be pushed proximally and rotatedaway from the locked position during insertion of the shank head intothe receiver, as shown in FIGS. 22A-22I.

The load ring may be pushed distally and rotated to the lock positionsubsequent to insertion of the clip ring, as shown in FIGS. 23A-23C. Insome cases, the load ring is rotated about a longitudinal axis of thereceiver, L1, for about 90 degrees from the open position to the lockposition. In some embodiments, the shank head is configured to be pusheddistally from the open position to the lock position subsequent toinsertion of the clip ring. The load ring may have an inner surface 503and a distal portion thereof accommodates a shape of at least part ofthe shank head. The load ring may include a top opening allowing accessto the shank head from a top of the receiver. The load ring can have anouter groove 504 between the pair of legs and a bottom portion thereof.The bottom portion of the load ring may be substantially cylindrical.The cross section at the bottom portion of the load ring can be greaterthan a cross section at the pair of legs thereof.

In some embodiments, the pair of arms comprises a protrusion 213 on aninner surface thereof, the protrusion 213 configured to prevent proximaltranslation of the load ring 500. As shown in FIG. 21B, at least part ofthe shank head may extend beyond the distal portion of the inner surfaceof the load ring when the bone screw shank is rotated from thelongitudinal axis of the receiver.

In some cases, the bone screws 100 herein include an iliac screw or asacral screw. The bone screw may comprise a tool engagement groove at anouter surface of the pair of arms at or near a top thereof.

Disclosed herein, in some embodiments, are methods for assembling a bonescrew 100. The methods disclosed herein may include one or more methodsteps or operations disclosed herein but not necessarily in the orderthat the steps or operations disclosed herein.

In some embodiments, a method of assembly of a bone screw 100 includesproviding a bone screw shank 300 comprising a shank head 301, providinga receiver 200 comprising a base 201 having a cavity 209 therewithin,the cavity configured to securely accept insertion of the shank headfrom a bottom of the receiver; a pair of arms 202 a, 202 b extendingupwardly from the base; and a rod channel 203 defined between the pairof arms. The methods herein includes providing a load ring 500configured to be bottom-loaded into the receiver prior to the insertionof the shank head, wherein the load ring comprises a pair of legs 501 a,501 b connected by two concave surfaces 502 a, 502 b at its proximalside; and providing a clip ring 600 configured to be inserted into agroove 214 located in an inner surface at or near the bottom of thereceiver thereby pushing the load ring and the shank head into an openposition that is proximal to a locking position, wherein in the openposition, each of the pair of legs 501 a, 501 b is at least partlyfacing an opening of the rod channel and each of the concave surfaces502 a, 502 b are aligned with the pair of arms.

In some embodiments, the methods of assembly of a bone screw 100 includeone or more of the disclosed method steps. The methods of assembly mayinclude loading a load ring 500 from a bottom end of a receiver 200 ofthe bone screw through a cavity 209 thereof prior to the insertion ofthe shank head, as shown in FIGS. 22A-22D. Loading the load ring caninclude twisting the load ring about L1 axis so that each of twoopposing concave surface 502 a, 502 b at a proximal surface of the loadring is aligned with an upwardly extending arm of the receiver andpushing the load ring proximally, as shown in FIGS. 22E-22F. Thetwisting may be of about 90 degrees. The load ring may be inserted withthe pair of legs 501 a, 501 b facing the opening of the rod channel 203as shown in FIGS. 22C-22D. FIG. 22C shows a cross section of thereceiver along E-E′ in FIG. 22D, and FIG. 22E shows a cross section ofthe receiver along C-C′ in FIG. 22D. FIG. 22F shows the cross sectionalong B-B′ with the bone screw shank. Subsequent to the top-loading ofthe load ring, the load ring 500 and the shank head 302 may be pusheddistally as shown in FIG. 22G to allow insertion of a clip ring 600 fromthe bottom. Subsequent to inserting the load ring, the methods mayinclude inserting the shank head into the receiver from the bottom endthereof till access to a groove in an inner surface of the receiver ator near a distal end thereof is open. Afterwards, a clip ring 600 may beinserted into the groove 214 in the inner surface of the receiver, asshown in FIGS. 22G-22I. The methods then may include pushing the loadring and the shank head back distally; and twisting the load ring in toa locked position so that each of the two concave surfaces at the topsurface of the load ring is aligned with an opening of the rod channelof the receiver, wherein the load ring and the shank head is locked fromdistal movement, as shown in FIGS. 23A-23C.

Uni-Directional Favored Angle Bone Screws

Disclosed herein, in some embodiments, are bone screws with the tulip orreceiver custom designed around the shank. For instances, the shank neckgeometry can be specifically designed such that the tulip or receiverhas a channel to allow the shank to move directionally within the tulipas well as to control medial to lateral and caudal to cranial angulation(e.g., along L3 axis). The tulip or receiver may include a sphericalpocket to match the shank head and may have threaded reliefs to allowthe bone screw shank to be top-loaded into the tulip or receiver withthreading on larger diameter screws, e.g., a diameter of about 8 mm. Theload ring may have a spherical pocket and collet style fingers that areundersized to impart a frictional fit on the shank head once assembled.The load ring also may have material relieved to aid in the favoreddirection angulation of the screw shank. Once the rod is placed andlocked down, the bone screw, the spinal rod, and the shank relative tothe receiver can be locked. With or without a rod placed in the rodchannel and with or without a lock screw placed in the receiver, thebone screw disclosed herein may provide a hard stop for the rotation onthe receiver. In some embodiments, the hard stop is where thelongitudinal axis of the receiver and the longitudinal axis of the bonescrew shank are coaxial. The hard stop provided by the bone screwdisclosed herein may allow for derotation movements without the need toprovisionally lock the bone screw, reduce a rod, or use an outer orinner lock screw to lock the shank relative to the receiver. In someembodiments, this design of the bone screw is simple in nature andrequires less steps when used in a surgical procedure where both favoredangle screws and provisionally locking screw requirements are needed.For example, in a neuromuscular scoliosis case, the bone screw may beplaced, the receiver may be rotated or angled in the lateral directionto facilitate rod capture in the rod channel, then rotated back mediallyuntil the longitudinal axis of the receiver and the longitudinal axis ofthe shank are coaxially aligned, then the receiver may continue torotate to the contra-lateral side for rotational correction.

FIGS. 24-32 show exemplary embodiments of the bone screws with a favoredangle. The bone screws 100 may include a bone screw shank 300 comprisinga shank head 302, a receiver 200 having a base 201 with a cavity 209therewithin, the cavity configured to securely accept insertion of theshank head from a top or proximal end of the receiver; a pair of arms202 a, 202 b extending upwardly from the base 201; and a rod channel 203defined between the pair of arms, wherein the base comprises a cut-out211 a and a recess 211 formed in a bottom surface of the receiver,wherein the cut-out and the recess are shaped and sized to allowangulation in a range of about 0 degrees to about 60 degrees, forexample, in a first lateral direction D1. In some embodiments, theangulation allowed is in a range of about 0 degrees to about 40 degrees.In some cases, the angulation allowed is in a range of about 0 degreesto about 45 degrees. In some cases, the angulation allowed is in a rangeof about 0 degrees to about 50 degrees. In some embodiments, the bonescrew shank can spin or rotate about L4 axis when the shank is rotatedabout longitudinal axis of the receiver, L1.

The bone screw shank can be configured to rotate about L3 axis, which isshown in FIG. 29. The L3 axis may be perpendicular to the longitudinalaxis of the receiver, L1, and the lateral axis, L2, of the receiver. Insome cases, the rotation may be before a rod is secured in the rodchannel. A maximal angulation, a, between a longitudinal axis of thebone screw shank, L1, and a longitudinal axis of the receiver, L4, canbe in a range of about 0 degrees to about 65 degrees. The maximalangulation between a longitudinal axis of the bone screw shank and alongitudinal axis of the receiver is greater than about 45 degrees, 50degrees, 55 degrees, or 60 degrees.

In some embodiments, the bone screw disclosed herein has about 0 toabout 60 degrees in one direction along the medial-lateral axis (e.g.,along D1 direction), about 0 degree in the opposite direction (e.g.,along D2), and about 0 to 60 degrees the cranial-caudal direction (e.g.,along L3 axis), or a combination thereof. In some embodiments, the bonescrew disclosed herein has about 0 to about 60 degrees in one directionalong the medial-lateral axis (e.g., along D1 direction), about 0degrees in the opposite direction (e.g., along D2), and about −10 to 10degrees the cranial-caudal direction (e.g., along L3 axis), or acombination thereof. In some embodiments, the bone screw disclosedherein has 55-60 degrees of angulation in the medial-lateral direction(e.g., along D1). In some embodiments, the bone screws disclosed hereinhas about −10 degrees to 10 degrees in the cranial-caudal direction.

In some embodiments, the distal geometry of the receiver may preventangulation of greater than about 0 degrees in a second or oppositelateral direction D2, e.g., opposite the first lateral direction. Insome embodiments, when a longitudinal axis of the receiver, L1, and alongitudinal axis of the bone screw shank, L4, are aligned, the bonescrew is configured to allow derotation movement in the second oropposite lateral direction. In some embodiments, when a longitudinalaxis of the receiver and a longitudinal axis of the bone screw shank arealigned, the receiver is configured to provide a hard stop to rotationalmovement of the bone screw shank relative to the receiver in the secondlateral direction, D2, without using a rod, a closure top, or any otherlocking element external to the bone screw. The angulation of the bonescrew shank may include movement in a medial to lateral direction (e.g.,along D1 and/or D2 axis) and/or movement in a cranial to caudaldirection (e.g., along L3 axis).

In some embodiments, a load ring 500 may be top-loaded into the receiver200 subsequent to the insertion of the bone screw shank 300 viatop-loading. The load ring may have a pair of legs 501 a, 501 bconnected by two concave surfaces 502 a, 502 b at its proximal side, asshown in FIG. 32. In some embodiments, the load ring 500 comprises a topor proximal opening 505 allowing access to the shank head from a top ofthe receiver. The load ring may comprise an inner surface 503 and adistal portion of the inner surface accommodating a shape of at leastpart of the shank head. The load ring can include multiple fingers 504at its distal end as shown in FIG. 32, and the fingers can be areconfigured to impart a frictional fit on the shank head. The load ringmay comprise a distal recess 506 at its distal end, the distal recessaligned with the recess 211 of the receiver. The distal recess may aidangulation of the bone screw shank, e.g., in the first lateraldirection, D1.

FIGS. 29-31 show different views of the receiver 200 disclosed herein.In some embodiments, the pair of arms 202 a, 202 b comprises a firstprotrusion 213 on an inner surface, the first protrusion configured toprevent proximal translation or movement of the load ring. A secondprotrusion 213 b may be distal to the first protrusion and preventsdistal translation or movement of the load ring. The first protrusionand the second protrusion may define a groove therebetween.

The receiver may comprise a pocket 212 in connection with the cavity ata distal portion thereof, the pocket 212 configured to receive the shankhead and allow directional rotation therewithin. The pocket may comprisea pocket surface having at least part of a spherical surface thataccommodates a spherical outer surface of the shank head 302. In someembodiments, at least part of the shank head extends beyond the distalportion of the inner surface of the load ring when the bone screw shankis rotated from the longitudinal axis of the receiver L1, e.g., as shownin FIG. 24.

The cavity 209 may comprise at least two bottom edges that aresubstantially flat, as shown in FIG. 29. Each of the at least two bottomedges are connected with a curved edge of the recess.

In some embodiments, the bone screw disclosed herein may be top loadedor bottom loaded during assembly. For top assembly, the bone screw shank300 may be top-loaded into the receiver 200. Subsequently, the load ring500 may be inserted from the top opening of the receiver.

In some embodiments, the shank head may comprise a head diameter or amaximal dimension in a range from about 4.0 mm to about 8.0 mm. The bonescrew shank may comprise a length, including or excluding the shankhead, from about 20 mm to about 120 mm.

In some embodiments, the bone screw may include a diameter of about 4.0mm to about 8.0 mm. In some embodiments, the bone screw may include alength from about 20 mm to about 120 mm. The bone screw may have about 0degree to about 60 degree angulation. Such range of angulation may be ina single lateral plane. In some embodiments, such range of angulationmay be in a single lateral plane. In some embodiments, the range ofangulation may be provided in more than one directions including but notlimited to the first lateral direction.

The bone screws disclosed herein may advantageously provide a hard stopat about 0 degree when the longitudinal axis of the receiver and thelongitudinal axis of the bone screw shank are coaxially aligned. Whencoaxially aligned, the hard stop may allow derotation movements of thereceiver in the direction opposite of the favored direction to aid forcapture of rods prior to derotation.

In some embodiments, the bone screw receiver disclosed herein may besized and shaped to include a different cut-out from that shown in FIG.29 so that the bone screw shank 300 may rotate symmetrically in twoopposite directions, e.g., D1 and D4. The bone screws 200 may beuniplanar bone screws that the screw shank 300 can rotate within asingle plane, e.g., a plane determined by L1 and L3 axes andperpendicular to L2 axis.

Referring to FIGS. 6A-6D, in a particular embodiment, the base of thereceiver 200 may include a cut-out 211 a that is sized and/or shaped toallow the bone screw shank 300 to rotate in a single plane determined byL1 and L3 axes. FIGS. 6A-6B are perspective views of the bone screw 100,FIG. 6C shows a cross-sectional view of the bone screw, and FIG. 6Dshows a perspective view of the receiver 200 with the cut-out 211 a at adistal end thereof. The cut-out 211 a may include two curved edgessymmetrically located at two opposite ends and each connected to thesame two substantially flat edges. The receiver may include two recesses211 that each works with the cut-out to facilitate angulation of thescrew shank about L2 axis. The screw shank may also be allowed to rotateabout a longitudinal axis of the screw shank, L4, when the shank isrotated by an angle away from L1 axis. In some embodiments, the sizeand/or shape of the cut-out 211 a, the recess(es) 211, or both may becustomized to control angulation of the bone screw shank from L1 axis.

In some embodiments, the angulation from L1 axis may be in the range ofabout 0 degrees to about 60 degrees. The maximal angulation allowed fromL1 axis may be in the range of about 30 degrees to about 60 degrees. Themaximal angulation allowed from L1 axis may be in the range of about 35degrees to about 50 degrees. The maximal angulation allowed from L1 axismay be in the range of about 40 degrees to about 50 degrees.

Polyaxial and Favored Angle Bone Screws

Disclosed herein, in some embodiments, are bone screws 100 having a bonescrew shank 300 comprising a shank head 302, a receiver 200 comprising abase having a cavity therewithin, the cavity configured to securelyaccept insertion of the shank head from a top of the receiver, a pair ofarms extending upwardly from the base, and a rod channel defined betweenthe pair of arms, a compression element 500 configured to be top-loadedinto the receiver subsequent to the insertion of the shank head. Thecompression element may comprise a pair of legs connected by two concavesurfaces at its proximal side, and a lock screw configured to betop-loaded into the receiver thereby locking the shank head relative tothe receiver.

FIGS. 33A-33D shows exemplary embodiments of different bone screw shanks300 compatible with the receiver 200 disclosed herein.

FIGS. 34A-34B show exemplary embodiment of top loading the bone screwshank 300 into the receiver 200 in cross sectional views.

FIGS. 35A-35G show an exemplary embodiment of top loading thecompression element 500 into the receiver 200 and rotating thecompression element into position relative to the receiver, subsequentto top-loading the bone screw shank 300. In some embodiments, thecompression element 500 can be loaded with each of the pair of legs 501a, 501 b facing an opening of the rod channel 203 as shown in FIGS.35A-35C. FIGS. 35A-35B are perspective views and FIG. 35C is a top viewof the bone screw 100. Referring to FIGS. 35D-35G, subsequent to thetop-loading of the compression element, the compression element 500 canbe rotated for about 90 degrees so that each of the pair of legs 501 a,501 b faces one of the pair of arms 202 a 202 b of the receiver, andpushed distally into a secured position relative to the receiver 200. Insome embodiments, the compression element is configured to be rotated ata first location proximal to a second location where the compressionelement is in the secured position, as shown in FIGS. 35D and 35G. FIG.35D shows a perspective view of the bone screw 100 and FIGS. 35E-35G areperspective views of the bone screw 100.

The compression element 500 can include a barb feature 515 on an outersurface of each of the pair of legs 501 a, 501 b. The barb feature canbe configured to interact with a corresponding protrusion 215 on aninner surface of each of the pair of arms 202 a, 202 b thereby allowingdistal insertion and preventing proximal movement of the compressionelement 500 relative to the receiver 200. The barb feature may include aramping edge on its distal side, which interacts with a complementaryproximal ramping edge on the receiver to allow distal movement of thecompression element relative to the receiver. The compression elementcan have a through bore from a proximal end to a distal end thereof, thethrough bore configured to allow access of a drive tool to the bonescrew shank. The compression element 500 may comprise an inner surfaceand a distal portion of the inner surface accommodating a shape of atleast part of the shank head. The compression element may comprise adistal recess 506 at its distal end, the distal recess aligned with therecess of the receiver when the compression element is in a securedposition. The distal recess of the compression element may be configuredto aid angulation of the bone screw shank, e.g., in the first lateraldirection. The angulation of the bone screw shank may include movementin a medial to lateral direction (e.g., along D1, D2, or both) andmovement in a cranial to caudal direction (e.g., along L3 axis). Atleast part of the shank head may extend beyond the distal portion of theinner surface of the compression element when the bone screw shank isrotated from the longitudinal axis of the receiver.

The compression element 500 or the receiver 200 may comprise a coaxialindicator configured to provide a feedback when a longitudinal axis ofthe bone screw shank, L4, is aligned with a longitudinal axis of thereceiver, L1. The feedback may be a tactile feedback. The feedback maybe prevention of rotation in a second lateral direction. In someembodiments, the cavity is sized and shaped to prevent pulling off ofthe shank head from a bottom of the cavity.

The bone screws disclosed herein may include a lock screw 710. The lockscrew 710 may be a dual lock screw as shown in FIGS. 35H-35L. The lockscrew can have an outer element 720 that couples with an inner surfaceof the pair of arms 202 a, 202 b, and an inner element 730 that isconfigured to be inserted within the outer element and couples with theouter element, e.g. via threads. Exemplary embodiments of the outerelement 720 are shown in FIGS. 35H-35L. The outer element 720 maycomprise a helical flange threadform 721 that couples with a matchinghelical flange threadform 216 on the inner surface of the pair of arms.The outer element may include an outer drive feature 722 at or near aproximal end thereof, the outer drive feature configured to engage adriver tool. The outer drive feature 722 may be located on an outersurface, inner surface, or both of the outer element. Referring to FIGS.35K-35L, in some embodiments, the outer drive feature may comprise ahexalobe at an inner surface of the outer element, the hexalobeextending distally but remaining proximal to a proximal end of the innerelement. The outer element comprises a protrusion 723 located betweenthe outer drive feature, e.g., the hexalobe, and a matching innerthreading 724 configured to couple to the inner element. In someembodiments, the outer drive feature may include an external hexalobe asin FIG. 35H, an internal octagon as in FIG. 35I, or internal hexalobedriver feature as in FIG. 35J.

In some embodiments, the inner element comprises an inner drive feature732, the inner drive feature configured to engage a second driver tool.The inner drive feature can include a second hexalobe at an innersurface of the inner element, the second hexalobe extending from at ornear a distal end to at or near a proximal end of the inner element 730.The inner drive feature may include shapes other than hexalobe that maycouple to a desired drive tool. The inner element may have an outerthreading 734 that couples to an inner threading of the outer element724. The dual lock screw can be configured to provisionally lock thebone screw head 302 relative to the receiver 200 prior to inserting arod in the rod channel of the bone screw.

In some embodiments, the lock screw 710 is a single lock screw. Thesingle lock screw can have a helical flange threadform 711 that coupleswith a matching helical flange threadform 216 on the inner surface ofthe pair of arms. The single lock screw may include a drive feature 712extending from at or near a proximal end to at or near a distal endthereof. The drive feature may be configured to engage a driver tool.The single lock screw may lock the shank head 302 relative to thereceiver 300 when a rod 400 is inserted in the rod channel 203 of thebone screw 100.

In some embodiments, the drive feature herein may be on an outer surfaceand/or inner surface to facilitate engagement with a drive tool withouteffecting coupling of the lock screw with the receiver. In someembodiments, the drive feature may be optimized in its shape and/or sizeto allow engagement with a specific drive tool.

The base 201 of the receiver comprises a recess 211 formed in a bottomsurface of the base, wherein the cut-out 211 a and the recess are shapedand sized to allow angulation in a range of about 0 degrees to about 40degrees. In some embodiments, the base and the recess are sized andshaped to allow favors angulation in a single direction, e.g., in thefirst lateral direction, or in a single plane. In some embodiments, thebase 201 and recess are shaped and sized to prevent angulation ofgreater than about 0 degrees in a second lateral direction opposite thefirst lateral direction. In some embodiments, the base and recess areshaped and sized to allow angulation in multiple directions. In someembodiments, the bone screw is polyaxial.

FIGS. 37-38 show cross sectional views of different angulation of theshank head relative to the receiver.

The bone screw shank may be allowed to rotate about a direction in whichthe rod channel extends, e.g., L3 axis, of the receiver. A maximalangulation between the bone screw shank and a longitudinal axis of thereceiver, L1, can be greater than about 50 degrees or about 55 degrees.A maximal angulation of the bone screw shank and a longitudinal axis ofthe receiver can be in a range of about 0 degrees to about 60 degrees.In some embodiments, the bone screw shank may be allowed to rotate aboutL1 axis of the receiver. In some embodiments, the bone screw shank islimited to rotate only in a lateral direction, e.g., in D1 direction asshown in FIG. 33B. In some embodiments, the bone screw shank is allowedto rotate along one or more directions other than D1, some or all of thedirections forming an acute angle with the D1 direction. In someembodiments, the direction of rotation is determined by connecting thelocation of the shank right before the rotation, and the new location ofthe shank right after the rotation within the plane determined by L2 andL3 axes.

In some embodiments, the receiver may comprise a pocket in connectionwith the cavity at a distal portion thereof, the pocket configured toreceive the shank head and allow directional or polyaxial rotationtherewithin. The pocket can have a pocket surface having at least partof a spherical surface that accommodates a spherical outer surface ofthe shank head.

In some embodiments, wherein the shank head has a head diameter in arange from about 4.0 mm to about 8.0 mm. The bone screw shank may have alength from about 20 mm to about 120 mm. A diameter or a maximaldimension of a cross section of the dual lock screw is in a range ofabout 5.5 mm to 6.0 mm. A diameter or a maximal dimension of a crosssection of the single lock screw can be in a range of about 5.5 mm to6.0 mm. The rod channel may be configured to receive a spinal rodtherewithin, wherein the spinal rod comprises a non-circular crosssection.

Unless otherwise defined, all technical terms used herein have the samemeaning as commonly understood by one of ordinary skill in the art towhich this invention belongs. As used in this specification and theappended claims, the singular forms “a,” “an,” and “the” include pluralreferences unless the context clearly dictates otherwise. Any referenceto “or” herein is intended to encompass “and/or” unless otherwisestated. As used in this specification and the claims, unless otherwisestated, the term “about,” “approximately,” “generally,” and“substantially” refers to variations of less than or equal to +/−1%,+/−2%, +/−3%, +/−4%, +/−5%, +/−6%, +/−7%, +/−8%, +/−9%, +/−10%, +/−11%,+/−12%, +/−14%, +/−15%, +/−16%, +/−17%, +/−18%, +/−19%, or +/−20%,depending on the embodiment. As a further non-limiting example, about100 millimeters represents a range of 95 millimeters to 105 millimeters,90 millimeters to 110 millimeters, or 85 millimeters to 115 millimeters,depending on the embodiments.

While preferred embodiments of the present invention have been shown anddescribed herein, it will be obvious to those skilled in the art thatsuch embodiments are provided by way of example only. Numerousvariations, changes, and substitutions will now occur to those skilledin the art without departing from the invention. It should be understoodthat various alternatives to the embodiments of the invention describedherein may be employed in practicing the invention. It is intended thatthe following claims define the scope of the invention and that methodsand structures within the scope of these claims and their equivalents becovered thereby.

1.-181. (canceled)
 182. A bone screw comprising: a bone screw shankcomprising a shank head; a receiver comprising a base having a cavitytherewithin, the cavity configured to securely accept insertion of theshank head from a top of the receiver; a pair of arms extending upwardlyfrom the base; and a rod channel defined between the pair of arms,wherein the base comprises a recess formed in a bottom surface thereof,wherein the base and the recess are shaped and sized to allow angulationof the bone screw shank relative to the receiver in a range of about 0degrees to about 60 degrees in a first lateral direction and preventangulation of greater than about 0 degrees in a second lateral directionopposite the first lateral direction; and a load ring configured to betop-loaded into the receiver subsequent to the insertion of the shankhead, wherein the load ring comprises a pair of legs connected by twoconcave surfaces at its proximal side.
 183. The bone screw of claim 182,wherein the receiver comprises a pocket in connection with the cavity ata distal portion thereof, the pocket configured to receive the shankhead and allow directional rotation therewithin.
 184. The bone screw ofclaim 183, wherein the pocket comprises a pocket surface having at leastpart of a spherical surface that accommodates a spherical outer surfaceof the shank head.
 185. The bone screw of claim 182, wherein the bonescrew shank is configured to rotate about a transverse axis of thereceiver in the first lateral direction before a rod is secured in therod channel.
 186. The bone screw of claim 182, wherein a maximalangulation between the bone screw shank and a longitudinal axis of thereceiver is in a range of about 0 degrees to about 60 degrees.
 187. Thebone screw of claim 182, wherein a maximal angulation between the bonescrew shank and a longitudinal axis of the receiver is greater than 55degrees.
 188. The bone screw of claim 182, wherein when a longitudinalaxis of the receiver and a longitudinal axis of the bone screw shank arealigned, the bone screw is configured to allow derotation movement inthe second lateral direction to aid capture of a rod.
 189. The bonescrew of claim 182, wherein when a longitudinal axis of the receiver anda longitudinal axis of the bone screw shank are aligned, the receiver isconfigured to provide a hard stop to rotational movement of the bonescrew shank relative to the receiver in the second lateral directionwithout using a rod, a closure top, or any other locking elementexternal to the bone screw.
 190. The bone screw of claim 182, whereinthe load ring comprises a top opening allowing access to the shank headfrom a top of the receiver.
 191. The bone screw of claim 182, whereinthe load ring comprises an inner surface and a distal portion of theinner surface accommodating a shape of at least part of the shank head.192. The bone screw of claim 182, wherein the load ring comprises aplurality of fingers at its distal end, and wherein the plurality offingers are configured to impart a frictional fit on the shank head.193. The bone screw of claim 182, wherein the load ring comprises adistal recess at its distal end, the distal recess aligned with therecess of the receiver.
 194. The bone screw of claim 193, wherein thedistal recess is configured to aid angulation of the bone screw shank inthe first lateral direction.
 195. The bone screw of claim 194, whereinthe angulation of the bone screw shank comprises movement in a medial tolateral direction, movement in a cranial to caudal direction, or both.196. The bone screw of claim 193, wherein the pair of arms comprises afirst protrusion on an inner surface thereof, the first protrusionconfigured to prevent proximal translation of the load ring.
 197. Thebone screw of claim 196, wherein the pair of arms comprises a secondprotrusion on an inner surface thereof, the second protrusion configuredto prevent distal translation of the load ring, the second protractiondistal to the first protrusion.
 198. The bone screw of claim 193,wherein at least part of the shank head extends beyond the distalportion of the inner surface of the load ring when the bone screw shankis rotated from the longitudinal axis of the receiver. 199.-252.(canceled)
 253. A bone screw comprising: a bone screw shank comprising ashank head; a receiver comprising a base having a cavity therewithin,the cavity configured to securely accept insertion of the shank head; apair of arms extending upwardly from the base; and a rod channel definedbetween the pair of arms, wherein the base comprises a recess formed ina bottom surface thereof, wherein the base and the recess are shaped andsized to allow angulation of the bone screw shank relative to thereceiver in a range of about 0 degrees to about 60 degrees in a firstlateral direction and prevent angulation in a second lateral directionopposite the first lateral direction; and a load ring configured to beloaded into the receiver subsequent to the insertion of the shank head,wherein the load ring comprises a pair of legs connected by two concavesurfaces at its proximal side.
 254. The bone screw of claim 253, whereinwhen a longitudinal axis of the receiver and a longitudinal axis of thebone screw shank are aligned, the bone screw is configured to allowderotation movement in the second lateral direction to aid capture of arod.
 255. The bone screw of claim 253, wherein when a longitudinal axisof the receiver and a longitudinal axis of the bone screw shank arealigned, the receiver is configured to provide a hard stop to rotationalmovement of the bone screw shank relative to the receiver in the secondlateral direction without using a rod, a closure top, or any otherlocking element external to the bone screw.